Rebuilding a Borg Warner T98 Transmission

Behold the mighty driver side PTO equiped T98! As found in my 1965 D1100 4x4, this transmission is the original model gear box for the truck however not original to this truck as evidence showed upon removal.

This unit displays several issues in that it leaks like a civil servant and also in hard shifting, making growling noises when being pulled into gear. This unit had a PTO that a shop removed several years ago in their laziness for not wanting to bend an exhaust around it. Its been sitting in a box since then. I will be performing a full overhaul with my transfer case now on the way back to the vehicle. Please note, I replaced my wheel missing in this pic, I wouldn't recommend doing this on stands of any kind other than a lift.

First up, removal, and PO forensics.
The first step is disconnecting everything and draining the oil, in my case a reverse circuit wasn't applicable, the 4x4 shifter must be unbolted from the passenger side (REPLACE THE BOLTS, THE HOLES AREN'T BLIND) and obviously drivelines must be removed, mine were already removed with my t-case. Up in the cab, there is a cover at the base of the shifter that must be removed, it can be missed if covered by mat, carpet, ect. Next I find the best way to get the shifter out of the way is to shift neutral and remove the lever from the top. The dome shaped cover at the bottom of the lever unscrews and the lever can be pulled out upwards, here take care not to lose the pin in the left side of the housing, it can fall into the trans. The last things holding the unit in the vehicle are 4 studs with nuts in the bell housing aft of the clutch. I found that a motorcycle jack was perfect for the removal process. I acquired this one from harbor freight for less than $80 with a coupon. To adapt the two pads on the jack to the trans, it was a simple piece of 4" thick laminated beam (several pieces of 4x4 board would work screwed together) with two 4x4 boards in front and behind the PTO adapter that hung down slightly. Because the bottom of the trans is not flat, there is a 1" thick slat used as a spacer in the back, and to begin removal, the jack is brought up easy untill the front block cant be moved by thumping a fist against it. Then the slat is wedged in till it no longer moves, again, thumped into place with a fist. I tensioned the jack a very small amount after that to relieve some weight. With this technique the trans was perfectly supported front to rear and in my case because I'm on gravel, the jack rolls on plywood straight to the rear.


With the jack supported the mounting nuts can now be loosened, two of my studs came with their nuts, you want the two top studs to remain in place wich mine conveniently did. These two help maintain alignment on the way out. The bottom two can be removed completely, I backed off the top two to the end of their studs, then, using a pry bar in the gap between the bell and the casing (shown above, just aft of clutch access) the trans started rearward quite easily.

This continues untill you build enough confidence in your jack to remove the last two nuts all the way. From here, the front bearing retainer slides free of where it bears in the bell housing, as seen here as that shinny edge centered between the bell and casing:

Now that everything is free (keep in mind adjustment of the jack may be necessary) the whole assembly should slide aft completely free of the truck and drop the throw out bearing in the bell housing.

The trans can now be easily lowered on the jack, one end picked up at a time and the blocks removed, then spilled off the jack. Note above the case is turned on its passenger side, I did not replace the 4x4 shift bracket bolts and residual oil went everywhere. After dragging my prize out one side of the truck, I noticed the oil spill was brass colored, upon closer inspection, evidence of metal particulate only got more obnoxious.


It did not end with brass either, here I found what appeared to be part of a gear tooth:

This concluded removal, stand by for forensics of a PO swap.
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With the trans out of the vehicle, I did some wire brushing to expose and clean up casting numbers before I quit for the day, the first swipe across a crusty T98 revealed a spot of yellow paint.
From the paint, I can only assume the original tired gearbox was replaced with another from an unknown international 1 1/2 ton truck that was in 'FAIR' condition. . . sure. . . . the front face of the trans was coated with antiseize of some kind, and removal was far to cooperative to be in character for this truck. Thus I believe the swap was relatively recent in the trucks life. Now, how did they know, that it was in fair condition? Well, removing the top cover of course! And just my luck, PO never put on a new gasket.

Notice above, the way the gasket was clamped in there by the dirt.
Anyways, doesn't make a hill of beans difference now, the problems with this gearbox are getting nuked out of existence. First step, as you guessed, pull the top cover, here we find an intimidating looking clump of gears; don't be afraid, its actually quite simple. First thing I did was count and inspect the first gear teeth. Given the evidence of a swap, I needed to rule out that it might be a t18. 43 teeth on the first slider so it is a t98. There are 43 teeth, but they aren't necessarily good teeth:

This is by far not the worst gear that can be found, this damage is the result of one of, or combination of things. Through wear, the pin that prevents the shift lever from rotating along with a couple other bits makes distinguishing third from reverse difficult when upshifting from second. *crunch* The reverse idler also takes some punishment from this obviously. The other thing is that people don't realize is that these spur type gears(both first and reverse) should NEVER BE SHIFTED TO WHILE MOVING!!! Again: *crunch* the first gear is the only gear besides reverse that actually slides completely out of engagement with the cluster gear, the reverse idler interacts with the same bank of teeth on the cluster gear as first, as well as first itself. The cluster and reverse idler can't be seen well from an assembled state, I got lucky and the cluster looks much better than the first slider. Reverse also looks better but still battered. After consulting with some experts over on BP, I decided to run the existing gears and clean up the jagged areas of the teeth.

Disassembly is not too hard. I would do one thing differently in I would remove the yoke at this point. I did it later on out of forgetting to remove it more than anything, it didn't hurt anything, it just would be much easier. The cotter pin is removed, and with it in neutral, an impact driver removes the nut with some pulsing of the driver. The socket I used was a Carlyle
*note insert size*
And required grinding down the outside to fit in the yoke.
Much more to come, stay tuned!
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I disassembled my gearbox on the ground next to the truck. DO NOT DO THIS, unless you are planning a full overhaul. Contaminants such as dirt, dust, and road grime are not conducive to proper lubricity and long wear life. Since I will clean everything inside and out, it's not a big deal. I will note if I had to do it again, I would've moved it to somewhere I could pressure wash it prior to disassembly.
I will also note that I did not follow the service manual exactly. I took some pictures of the needed pages to reference from my phone during disassembly, since my phone is much easier to degrease than paper, and less susceptible to wind(remember I'm outside in a car tent, wich doesn't do much to stop wind).
The first step in disassembly is to remove the yoke as noted before, then I cracked all the bolts lose with a bar before proceeding. Next up, the top cover is removed. At this time I performed the previously discussed inspections and took some pictures of the safety wire arrangement in the shift fork/bar assemblies.

Once the wire is documented and can be easily reproduced, I cut them free with some dikes and began loosening the tapered square head bolts that locate the forks. First to go is the 1st/2nd fork, wich slides free of the bar easily.

At this point I found it prudent to remove the frost plugs. The first three are the ones at the rear, wich I drove out at an angle with a plastic mallet and a rachet extension(for the rounded corners). Once these are gone, the shift bars can slide to the rear fully out of the top cover once free of the other parts. The next part to come out is the tapered screw for 3rd/4th wich allows this shift bar to move rearward free of the top cover.

Be careful here as there is an interlock pin in the shaft you wont want to loose in addition to the poppet ball and spring. I held my dikes over the hole just because it was so difficult to get the shift bar to depress the poppet ball out of the way I thought it was under sufficient spring tension to hurt my hand upon flying free. In reality it was a buildup of metal particulate sludge at the base of the spring, no doubt not helping the hard shift issue. These can however still fly away with sufficient force, so wear some eye-pro, you may thank yourself later. Next the other two shift bars can freely move and disassembling them follows the same path as the first minus the interlock pin. Tapered screws removed, they slide free of the housing dropping their applicable interfaces and releasing a poppet ball and spring.


The above images show removal of the reverse side, the part in the second pic is where the end of the shift lever interfaces with the shift bar. The round plunger is spring loaded and in addition has its own poppet ball and spring that interfaces in one side of it. This gives the leaver the spring loaded effect when shifting into reverse, and these parts if worn enough can permit unintentional gear clash when reverse is mistaken for third on an upshift. This sub-assembly will be further disassembled later. At this point, the top covers remaining shift bar is removed the same way as the others, and the front plugs can be driven out with a punch and plastic mallet from the inside where the shift bars were. Lastly, there are two interlocks between the three shift bars. They live between where the poppet balls and springs are housed and are retained by goop. Be sure to save those, they can be pushed out with an allen key. With that, the top cover is completely disassembled. The only remaining shift fork resides in the transmission case, and operates the reverse idler. It is removed by driving out a pin located on the outside of the case as shown here:

From within the case, the pivot point of the reverse fork can be pushed outward slightly then pulled free by hand from the outside:


Above we see a tired rubber O-ring no doubt a contributing factor to the leaking problem. Once removed the reverse fork can be removed:

With all the controls removed, along with that pesky yoke I forgot, its now time to begin on the transmission core.
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For the lower case and gearing, the first step is pull off the front bearing retainer and remove the bearing. The retainer is easy enough, four simple bolts are removed and it slides off the end revealing the bearing. The bearing has a spacer and snap ring on the outside of it, and it can be accessed with a puller (that i don't have) by pulling the shaft forward after a light thump on the end with a wood block.
The input shaft is a tight fit inside the bearing, the outside is not tight to the case. Thumping the shaft rearward presses the bearing off the shaft slightly as it bottoms out against the snap ring and spacer. The problem is eventually the shaft bottoms out as well. So here, again, i don't have the right puller, I used a kind of hillbilly tactic, spacers that gradually increase in size
Untill those spacers weren't big enough anymore, so I got even more hi-tech:
In the last pic the bearing finally came loose by hand. This technique may make some cringe but keep in mind the amount of force needed to move the bearing in this case wasn't much. Just the weight of the wood block I was using swinging my arm under gravity made more than enough progress to be effective. I would NOT have continued if more force was required in moving the shaft out of the bearing. Now we see some lovely, clean(for a change) IH part markings:

At this point I was fed up with the case sitting at an awkward angle and removed the pto cover and subsequently the adapter/idler housing:

Once free there was more evidence of damage, this time more severe in the bottom of the case and caked against the pto cover:
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Cleaning that out, I replaced the cover on the main housing to prevent spillage of sludge and rollers later on.
With the case now finally sitting a bit more solidly I removed the rear bearing retainer, speedo drive gear(??? I thought it was 4x4! Oh wait... At least PO had the decency to find an actual cap screw rather than leave the speedo drive open into the case)


The output shaft can actually be pulled rearward by hand enough to get at the bearing. Now in this case I had a puller that would fit, although admittedly not the greatest one ever:

Once the bearing came loose it displayed the same nice markings as its friend up front.
The upper hunk is now free to remove, the input cluster actually pulls away from the output cluster(wich is obnoxiously heavy, hence the lack of pics here) dropping its rollers into the case and allowing the front of the upper hunk of gears to lift up in front and slid out of the assembly. This portion will be disassembled later.
With that out of the way the input shaft is easily plucked from the case, the rollers are recovered later on:

Next up the shaft retainer is removed and the cluster gear's idler shaft is, for lack of a better term, BLUDGEONED VIOLENTLY from its home, with a brass punch as the moderator/mitigator of abuse:

Above can be seen the retainer I used as a handle to pull the shaft free by hand. A look through the bore shows enough rollers to be mildly terrifying before the cluster is pulled:

I accepted fate and just dumped the cluster's contents into the case for later recovery:

For a device that has always intimidated me, its surprisingly easily disassembled and understood. Short of this, i honestly don't think I think I would've ever been able to figure out how one worked. More to come in the next two installments, stand by for complete disassembly! :icon_rotate:


The last hunk to come out of the case is the reverse idler, wich is retained by another shorter idler shaft. Disregard the directions in the service manual and proceed as follows. You will need, a nut, a bolt, a washer, and a piece of pvc pipe. They are arranged as a jack, the nut is loosened off the bolt wich pushed the washer and pipe like a press. This arrangement presses the idler shaft right out.

The reverse idler gear retains all its rollers within it, and lifts out with the shaft removed.

Now. The fun part:

The first synchro ring falls off the end, and next up is a snap ring, wich is followed by the synchronizer unit and third gear.

The brass synchro ring lifts off of third gear, and the synchro unit has two spring rings in each side that easily remove before the outer body of the synchro unit is pulled off the inner body. Once they are separated it will permit the three stamped detints to come out of the center body of the synchro unit:


Next at the other end of the shaft, the snap ring is removed, allowing the 2nd gear synchro/1st sliding gear assy to slide off dumping the second gear rollers:
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Once these items are removed from the shaft, the last part left is a snap ring. The 2nd synchro ring is then easily plucked from the 1st slider/second synchro group. Here I found increasing evidence of metal particulate:


To disassemble the first slider from the center hub, it is placed on a block to support the center, wrapped in a towel to prevent loss of poppet balls and the 1st slider gear is pressed down off the center body:

Here I found even more evidence of metal particulate, that had made a sort of cement with oil as a result of a centrifugal effect(only found in inside facing pockets and surfaces):

This material is very difficult to remove in a non messy way and once displaced has a property similar to glitter (DO NOT GET THIS IN YOUR EYES, oil in general would be bad, this would be far worse). With all of that done, disassembly is complete. The third gear bushing looks to be removable, however I have no reason to remove it and there is likely not a replacement available.

The next step from here would be disassembly of the pto, however there are so many important tech details accumulating (on what is in reality an incredibly simple component) I think its best to tackle that one once the trans is done as a separate rebuild farther down this thread or as a separate thread entirely.
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New member
Thank you for posting this. I am currently in the process of rebuilding a T-98 and am fumbling along. Have you begun the rebuild yet?
Yea, this is quite a bit farther along than this thread, it will be getting an update and some edits at the end of the week. If you need info, send me a pm, I'd be happy to help. Currently I'm about halfway through cleaning and paint prep.
Overdue update time! A few important points before tackling cleaning. First up, a fairly severe case of worn shift alignment pin along with socket damage.



The socket that the shift lever pivots in has a pin in the side that keeps the lever from rotating. In this case, the pin is harder than both the pivot in the shift lever and the top cover itself. Not only is the pin hole worn to the extreme and the surrounding metal cracked in a couple spots, the hardness of the pin has distorted the slot in the shift lever pivot. This raised a large bur over time resulting in a massive cavity growing around the pin hole as seen above. This is a large contributing factor to sloppy shift pattern.
In addition, several other factors can contribute, the shift bars fit to the tapered screws, the interfaces that join the shift bars to the lever both in their fitment on the shift bars as well as wear on the engagement surfaces that the lever bears against. In addition, the forks themselves can wear thinner than preferable. The solution in an ideal world would be new replacements. Sadly we live in the pessimistic and sad world devoid of oem parts known as reality. So here we rely on luck. Cast metal, while not impossible to weld is difficult at best. The t98 is largely obsolete, wich leaves us refurbished and used parts. . . .

And so I bought another top cover.

The pivot socket, while still worn, is in much better condition than mine along with the pin hole (still needs repair). My plan that I am currently exploring is to drill the original hole to round, use that size drill bit shank for a new pin, with the lever cut widened, then drill the other side and slot the opposite side of the lever pivot, effectively doubling the alignment pin's strength.
In the new top cover, I actually lucked out in that the lever interface parts were the mirror opposite of my wear pattern. Here you can see the two reverse interface parts, my original the one with the shinny rounded off edge the other is from my new top cover:

The forks on the donor are much more worn than mine, the tines are about 25-30 thousandths thinner than my original forks. In addition, the 3rd/4th fork that doubles as the shift lever interface is in much better condition on my original. Therefore I will simply reuse the originals.
Originals are right, donor spares are left:


Interestingly the interface fitment of the 1st/2nd interface was the polar opposite of reverse for the two assemblies,
My assembly was fine, while the donor was badly gouged. Fitment of my original tapered screws in my original shift bars was very tight, and I wont be messing with them. I kept the screws in the part they were in to ensure they go back in the same hole, when I reassemble I will simply swap the required parts.

In addition to these parts, a basic set of consumables is required. The parts are found in a top cover small parts set, which I sourced as a ford t18 top cover kit. There are fork bushings included that the t98 wont need, along with the large roll pins used to secure the t18 forks. There is also a round gasket used to seal a reverse switch wich I hope to add to my rebuild. The kit includes a bag of expansion plugs, the three interlock pins, the shift alignment pin (oem size) three poppet ball/spring sets, the reverse plunger spring, the reverse plunger retaining clip, and the large spring for the shift lever seal:

While we're here its a good time to point out that I've found some information that implies the poppet sets for the top cover and synchro clutch are the same parts, and I'm looking into that further currently. Now the remaining parts can be cleaned, gears and internals I personally prefer to leave oiled and wrap in rags or shop towels and store untill just before reassembly when I then clean them. The external housings and covers I will cover briefly here. I cleaned the outside for dirt and loose paint first by wire wheel. Once the outside is roughly clean, I filled a large heavy plastic storage bin with five gallons of diesel. I left the main case in there for about a week, rolling it around to a new side once or twice a day. This allowed the metal particulate sludge to loosen as the thick 90wt thinned in the diesel. At the end of this stage, dunking the case by hand repeatedly rinsed most of the particulate out of the housing and further rinsing with brakleen removed what was left along with 99% of the diesel. From here, I used shop towels and old used acetone to float off the majority of the paint. A more aggressive wire wheel job took care of what was left. The process was the same for the top cover. Twice. (I decided just before paint to replace the cover) I use a dremel tool with a small wire wheel to get in the hard to reach areas. The new top cover has a bit of rust, I plan on soaking it in evapo rust pre paint.
Once generally clean, I mocked up the retainers, top cover, and my pto adapter housing to inventory my hardware. All bolts and washers I'm replacing with new grade 8 zink flake coated bolts and Nordlok washers.

Now to paint prep and paint. The front and rear bearing retainers and yoke I did in a cardboard box, red oxide primer followed by IH red for the retainers, black for the yoke. The main case on the other hand required much more finesse. The first paint prep step was to thoroughly clean all the threads, wich I did one hole at a time with some cheap .38/9mm and .30 cal pistol/rifle bore brushes, acetone, and some rags. 99% of these holes are pass through and must be CLEAN to ensure seals. I kept track one hole at a time using a marker.

Next I used shop towels and clean acetone to wipe the entire case clean. I then removed lint from the shop towels with a clean stiff bristled paint brush. Now the clean work/paint environment is essential to good paint, so final cleaning and taping was done on a clean folding table in my garage right before moving it to the paint area.



Now to the paint booth! But wait, too poor for a paint booth? Look no further! The ghetto paint booth returns!

Important note: DO NOT VACUUM PAINT FUMES! This vacuum has a second hose port allowing it to blow filtered air. So, clean bag, cleaned out hose, a vent and Bob's your uncle!

Some time later:


When in the sun, internal temperatures reach roughly eleventybillion degrees, wich helps the paint dry quite quickly. As always, refrain from standing in front of the blower tube. It may feel good in the heat, but its not worth the time it takes to clean the bright red butt print off your nice craftsman garage stool. :mad2:
To be continued. . .


Active member
Have you ever tried oven cleaner for removing grease, oil and paint prep? It works great and the grease washes away with water. Easy Off is the brand I use. Paint sticks great the etched surface it leaves.
With paint completed, I set the main case on a series of folded cloth and foam pads, and completed one final mock up with gaskets in place.

There were several small issues I found here, most of which we'll rectify later on in another post. Important to note now, are to do with completing all the parts and mods before assembly so it can be assembled as quickly and as cleanly as possible. The rear bearing retainer of this transmission had several variations, and the included gasket just barely doesn't cover a small inner protrusion, creating a path into the casing for water or vise verse for oil at the top of the rear retainer. Visible on the right side here:

The rebuild kit I purchased from IHPA contained the following:

input shaft rollers
countershaft rollers
front and rear seals
front/rear retainer gaskets (several variations)
top cover/pto gaskets(several variations)
front/rear main bearings
Set of snap rings with a spare in two sizes
Set of countershaft roller spacers
Front/rear countershaft thrust washers
Front/rear main bearing seat ring thingys :confused5:
Front main bearing oil splash shield

The following items I feel really should've been included but were missing:

top cover parts kit
Reverse gear rollers
2nd gear rollers
Reverse lever pivot pin's seal and taper pin
Synchro poppet balls/springs

The only other noteworthy mentions are that the rear retainer gasket in the correct variation was not included(not a big deal) and the rear main seal was not the right size.

Though there were obvious problems with this kit, it's important to have this context and in my opinion the kit in my case does not reflect on IHPA or specifically the kit itself. I purchased this kit over a full year in advance of removing the trans. I entered the details of my truck, 1965 1100 4x4. This trans I found to be a swap, quote the yellow paint "68 ihc 1 1/2 ton" iirc with no other known details about that truck.

In addition, by the time I realized pieces were missing to such an extent, the covid lockdown was already in full swing, and IHPA had just announced running with limited staff. So rather than take up their limited time I chose to find the parts myself, as I was in the middle of reassembly prep and felt I could get it done faster. I have no doubt that IHPA would've rectified the issues described here had I given them the opportunity to do so. I felt confident I could find what I needed myself and just didn't want to bother them.

Once I figured out what I needed to track down, all it took was a bit of research to find part numbers for the rollers:
Q-6086 for 2nd
B1316-Q for reverse.
These as IH are obsolete. Sort of. There are part#s that manufacturers of other parts that use these rollers used as replacement equivalents, and that's what these are.

The misfit gasket can easily be made. The tapered pin for the reverse lever pivot in my case was reusable, and it's seal simply a matter of finding the right O-ring. The synchro poppet balls and springs I sourced together with some other parts that I'll go over now.

In preparation for reassembly, smoothing out the chipped gear teeth is necessary to ensure the gears will slide into engagement easily) Chipped chamfers at the end of the tooth can bind on the other gears teeth when shifting. Keep in mind, these gears are meant to be stopped when shifted. The chamfer is meant to allow the teeth to align when slid together. I simply used a dremel tool and a grinding stone to smooth them out. The respective 1st gear on my countershaft cleaned up easily. Reverse took a bit more work. The first sliding gear presented some problems. At first I thought it would just take a lot of grinding but upon close inspection with my dual optical scanners under strong light, it seemed there were a lot of very subtle cracks down in the chips. Time to find a new first gear. Eventually I got in touch with a local transmission parts supplier who sourced me a nice used first gear, poppet balls/springs, and a brand new (old stock) un-bent shift lever.

For a repair on the shift lever alignment pin, a handy friend of mine pointed out that the wear issue is obviously due to the pin being glass hard. So, he reasoned, why not make the pin the weak link and a maintenance part? Not a bad plan. The pin's hole is worn a bit over size, but a taper pin in the right size and cut to length will work perfectly. Especially after I fit the hole with a tapered reamer. The outside of the pin can be fitted tightly to be retained by the cap. When the shifter gets sloppy, the pin can simply be pushed out and replaced from inside the vehicle with the unit in place. This also lessens the danger of the pin falling inside the trans during maintenance as it can only come out one way.

I was planning a couple modifications to the top cover when I got carried away with assembly. So I'll address those first here. If you want to do either of these, do yourself a favor. Don't begin assembly yet. . . cleanup was interesting.

1. reverse light switch
The first mod is getting shelved for later, but it's simple enough to attach once I'm ready. All it is is a simple bored out stud, threaded into where the aft freeze plug of the reverse shift bar resides. So all that's necessary for it is to drill and tap the hole.

The stud is adjusted close to the end of the shift bar when shifted into reverse, and thus the bar depresses a pin, held in place by a head on the outside of the case(picture a blunt tipped nail) over the head of the nail, a coupler is threaded on and into that is a 20amp pressure switch. The 20amp rating ensures I can run a more powerful light if I want.

What's more is that this mod isn't permanent. If you want, you can still install the freeze plug as the shoulder is not fully bored out. I plan on capping mine with a bolt for now, as its a bit big of a job for my bench top lathe to bore out this long/hard a stud. So I'll make that pass through stud once I have a proper full scale lathe. Or find a suitable part pre made.

2. Air vent extension.
This idea I actually stole from Big Ed over on binder planet. The original press fit hole is drilled and taped to fit a barbed hose fitting. This allows you to route the vent of this as well as the t-case and axles to one high up location on the fire wall. This keeps the sudden vacuum caused by rapid cooling from pulling water through the vent when you splash through deep water.

Lastly, before assembly, a clean area and an open source (finger dip) of gear oil are prepared. All internals are coated inside and out as they are assembled. If you plan on leaving the unit empty for an extended period of time, slather some oil on the insides of the case to prevent rust. Also, if that's the case, add the drain plugs and snug them down.

Lot's of progress to post, just haven't had the time to type it all out lately. Stay tuned for transmission assembly, plumber style! (Meaning I had none of the right tools) :icon_rotate::icon_rotate::icon_rotate:
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Moving into reassembly, I'll point out you will notice the first sliding gear change color later on in this thread. This was because I began reassembly while I was waiting for the new gear to arrive in the mail. I simply removed the first gear and hub off the end, dumping the poppet balls and springs and slid the new into place with the same method as assembly for compressing the poppets and springs, then reattached it. This hunk is listed in the instructions to be assembled after the 2nd gear but it doesn't to hurt to leave this for last.
One other note, if you do this on a folding table, before assembling the gears into the case, move the case over the table frame with one leg under it. That will support the weight. Virtually anywhere else on one of these tables wont.

Starting off, I got the complicated bit done first. With a bowl of 90wt oil, I just coated everything as I assembled. First up I assembled the first sliding gear onto its hub. There are supposed to be witness marks on the gear and hub for clocking, but they were absent from mine. I found that the poppet balls make wear marks inside the gear and these can be used to find marks that are hard to see as you have three possible ways to clock it. Something that appears to be just a scratch may be the witness mark if it continues onto the other part. This was not the case for me. So I assembled it and moved on. I will address a way to properly clock this with missing marks or when installing a used gear next post.

To compress the poppet assemblies, I first determined which direction the hub and gear go relative to each other. Then, set the gear down and put some spacers in the middle of it to hold the hub up in such a way that the springs were pushed above center of their hole as seen here:

This holds the plate in place and there is just enough give in the spring to add the ball and push it into the hole via thumb. It is then pushed down by the rectangular plate with a puch and the whole thing slips inside the gear and is retained like so:

Once you do all three you just pull the gear up onto the hub; the poppets find their detint pockets and hold it all together.

Next, add the first snap ring and spacer ring to the output shaft:

Then the Q-6068 rollers for 2nd gear are prepped, and third gear is assembled. I found the easiest way to do this was to hold the shaft on end, place the gear on the spacer washer with it eyeball centered, then add the rollers a few at a time with plenty of oil. Once you get a quarter of the way around, you can press the gear and those rollers against the shaft and it centers it the rest of the way, allowing the remaining rollers to slip in all the way around.

34 per the parts manual. These came in a pack of 36. They simply slip into place a few at a time, I dipped them all in oil as I added them.

Then the spacer is added:

Followed by a snap ring in the groove directly above the spacer.

Next the first gear assembly can be slid into place. I will note this isn't totally necessary to be done in this order. It would've been easier to add this hunk last as we will be working on the other end mostly. Notice my first gear is removed again:

I actually ended up removing the hub again later. . .

Moving on from there, the 3rd/4th gear synchro hub is then assembled. Again take note of the clocking witness mark. If not present I would make them using center punches, or a file pre cleaning. The hub is assembled by first clocking the two main parts, then adding the detint pieces, followed by the two spring rings:

Once complete, 3rd gear with its brass bushing is added to the shaft, followed by a synchro, the synchro hub assembly and a snap ring:

Note above, and with either hub assembly, the direction of the inner hub and outer ring(or gear in 1st's case) is noted in my disassembly pics, and replicated.

Now that that's done, the other end of mine came back off as I got my replacement gear in the mail. That whole first gear hub assembly is reassembled the same way as before and then reattached. At this point this subassembly is complete.

Stand by for more!

Now with the new gear assembled onto the hub, I put it in the shaft and assembled it stood up as shown here:

From here I measured runout to ensure the gear was properly mated to the hub:

I used the internal wear lines from the poppets to select one of three positions to start. I got lucky and found runout was within a couple thousandths all the way around measured first from the top of the gear teeth, then in between, then from infront of and behind the teeth. If it had more runout I would've just played with the clocking of the gear to the hub untill it was satisfactory.

Now that that part is done, I wrapped it in a cloth to keep dust off while I worked with the countershaft. They say to use an aluminum slave pin to hold the rollers in place, but I didn't have one, so a wood dowel in the same dimensions provided in the shop manual worked fine after a good sanding. I coated it in oil and let it soak in before use.
There is an important bit here, some of the T98 transmissions had a countershaft that was slotted for two tabs in one thrust washer. Others such as mine did not. The only thrust washer still available is the tab type, and they must be ground flush in order to fit properly. Here are the two compared:

Here it is after modification:

Once this is done, assembly of the countershaft into the case begins. The dowel is passed through the center spacer tube and placed in the countershaft's bore. I found the best way of doing this is to have the spacer tube off set toward the side you start on and push it farther in as you go. With the spacer visible in the bore, you add:
1 spacer washer
1 row of rollers
1 spacer washer
1 row of rollers
1 spacer washer
Repeat on the other side.

Once all the rollers are in place, the thrust washers are 'glued' in place with a grease that is safe on yellow metals. I used the same Lubriplate grease from my np202 rebuild thread.
The first washer is more easily installed inside the case:

The rear of the assembly has two washers, one is attached to the end of the countershaft, the other to the casing:


Now, remember I said the hard part was done? Well I lied. You now get to slowly slide this whole thing together without disturbing the washers, hold it there, AND slide a large shaft through it. It will take several tries. I did not yet fully seat the shaft in mine.

Next is the reverse gear. I will go over roller replacement and installation into the case.

"See? Transmissions aren't all that complicated after all." -Me 2020 right before I realized I left a part out. :lol:


For rebuild of the reverse idler gear, disassembly requires at least one of the snap rings be removed. I did both, as I found a lot of fine metal particulate that I wanted to ensure was completely gone. Once removed the guts simply dump out.

Here are the pieces ready for reassembly with the 74 new B1316-Q rollers post cleaning. First one snap ring is installed:

The gear is turned over and one washer is set in the bottom, resting on the snap ring. Now the center tube can be added and eyeball centered, followed by some of the rollers. Once you go a quarter or so around, the center tube can be pressed into that side of the gear's bore as the remaining rollers are added:

Once one full row is complete, the spacer is added followed by another row of rollers and finished with the second washer, retained by the second snap ring:


Now complete, the gear can be added to the case. First I ensure the longer shaft is clocked properly with the retainer plate:

Then the gear is simply lowered into the case, large teeth bank to the rear, and the shaft slid through:

Again, with the shafts loose, ensure proper clocking for the retainer plate like so:

Now they are ready to be driven home. To add a little extra leak prevention, I used my gasket adhesive around the shaft where it seats in the case near the retainer, and carefully painted some into the bore at the front. The reverse idler shaft only needs this at the back.

Technically they should seal by themselves, I just wanted to make darn sure. I set the trans in my shop press on the mounting face, and used a piece of nylon cutting board as a pad between the paint and press arbor.

Now the retainer plate is added, the bolt threads painted with the sealant, and torqued accordingly.

Next up, we get our inner plumber on! Also, blacksmithing sort of. . .
Remember me referencing the hard part again? Weeeeeelllll. . . This is more difficult than anything, in an irritating way.

First up, the input shaft with its synchro and rollers are assembled. The rollers are glued in once again with the aforementioned grease:

Then you just kinda add this in here half arsed looking like this(don't worry it's supposed to go this way):

Then this heavy hunk we assembled earlier goes in and rests on top of the counter shaft. The shaft end goes through the hole for the bearing and then the front is lowered to rest behind the input shaft:

Then, being very careful to avoid disturbing the rollers, and with a bit of oil in the end of the output shaft, you plug the two together, and add the rear main bearing:

Now, a note on the main bearings. I checked their fit on the shafts and picked the looser of the two for the front and left the other for the rear. The fit to the shaft is more important in the front that it be a bit loose to ease installation. If the rear is tight, it can be tapped in with a plastic mallet without much danger of compressing the synchros. This is not the case when installing the front. You can also use a bearing heater to expand the inner part in either case, but I don't have one. The rear bearing and retainer is needed to stop the axial sliding of the input/output assembly during installation of the front bearing. Next, the rear bearing retainer is installed with bolts evenly, and hand tight, no gasket. This ensures the bearing can't back out as we install the front:

Now, the front main bearing must be pushed into place. This is where the factory's special tools came in.

It's important to understand this to picture what you're trying to prevent during installation.

Note these points:

The synchro's inside surface is a tapered thread, and engages a hardened steel cone.

With oil in there, pressure from shifting causes a braking effect to 'synch' the gear with the ring that the fork engages.

Herein lies the problem:
You're about to play whack-a-bearing on the end of a sort of steel/brass ring sandwich that now has no give behind it, and those steel cones that mate with the synchros will squash those fragile brass threads without a second thought if given the chance.

The factory used a special spacer tool to slip behind the flat back sides of the synchros between the synchro itself, and the respective gear, thus the cones cant touch the threads no matter how much whack-a-bearing you play.

Like most things IH, the tool is obsolete and nowhere to be found, so I made my own. . . Literally anyone with an anvil (or equivalent), hammer, and wire cutters can make these. It all starts with some of that old coper water pipe from your bathroom remodel you probably threw away. Cut some pieces of it, open it up to a square, and leave it in CLR to clean it up.

Once clean, fold it a few times:

And bend one end into an L shape. Repeat once for each side of each synchro. The only criteria for these is that they be thick enough to space the synchro out of contact with the cone under pressure, so with that said, I made sure these had no give in them. The last part of flattening them was with my 40oz cross pien.

To seat the bearing, these (6) shims are put in place:

The oil splash shield is placed behind the main bearing, with the outer stepped edge extending away from the bearing. The spacer ring is added to the bearing behind the seat ring and the bearing is started by hand as best as possible. . . and then, plumber power!

Now the hard part is in fact done!
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With assembly nearing completion, the reverse lever goes in there at some point along the way. I actually installed mine between main bearings while I was figuring out my front bearing install method. The pivoting interface on the end engages like so in reverse gear:

And the lever's pivot is put back with a new O-ring, and the tapered pin to retain it.
With exception of the bearing retainers and gaskets the bottom half is pretty much complete. With this tech finished, I will turn my attention to the top cover. Once I finish covering it's assembly, I will cover final sealing of gaskets/torquing.

There are several small pins and plungers to take careful note of. The first shifter bar to install is the center bar that controls 3rd/4th.
Here can be seen the orientation of the bar with the pass through hole for the interlock pin shown near the end of the shaft. Be sure this is in place upon assembly, it can be secured adequately with gear oil:

A poppet spring and ball are placed into their pocket, and compressed with a large punch about 75% or slightly less of the diameter of the hole:

Once the shift rod is passed through the shift fork, the punch compresses the ball on the spring. The shift rod is held in place by hand pushing the punch against the other side of the hole, then the punch pulled out and the rod pushed over center of the ball with a blow from a mallet. It takes two people to make it easy. When you pull the punch out, be careful, as the spring under the ball can still push the shaft out of the way and fly out. Be certain there are no pockets in the shift rod on the side the ball is pressing against. Get the bar in place, and rotate the bar untill you can put the tapered screw in place on the shift fork.

Next, an interlock plunger is placed in the bore between shift bars:

The first shift bar must be in neutral position to allow the next bar to push this plunger out of the way. The shift bar is installed the same way as the first with its respective interface and the 1st/2nd fork:

Next comes another interlock plunger, again, both the other shift bars must be in neutral for the next shift bar to push the interlock plunger out of the way.
The reverse interface plunger is passed through the new spring, and can be held into the casting by hand to put the C-clip on. The detint ball is put in the bore ahead of it's spring, which I compressed on one side and captured with the cotter pin from the other.


The shift bar is installed the same way, take care to align the corner of the interface in the machined track in the side of the top cover. Also, there are all sorts of cuts in this bar that the poppet ball would just love to jump into. Pick a side of the bar the is solid all the way down, and rotate it after it is fully inserted to align the hole for the tapered screw in the interface.

Following this step I'd recommend making DARN sure you did everything correctly before installing the expansion plugs and safety wire. Now is a good time to oil the forks up and bolt the assembly onto the main case, put in the shift lever and try it out. . . Hey! What do you know, it's a transmission again! :yikes: