T407/TF 727 DIY Reseal

[Michael Mayben]

Look careful inside the hub of the pump body...ya can see the bushing. That is a tri-metal type bushing, very similar to a full shell cam bearing in an engine. Steel backer, then a couplea layers of copper/babbit and a oilite bronze wear surface.

The bushing in t's tranny has been replaced fairly recently with an aftermarket item. That one has a wear surface that is "dimpled" for lube oil retention and appears to be perfect. So in this one instance, I'm not going to replace it. In normal tranny seal replacement, and of course during an overhaul procedure, this bushing would be replaced.

 

[Michael Mayben]

Here's a typical replacement part seal, these are available under many different "brand names", name don't matter as long as the seal is the correct application. This happens to be a timken brand..."made in taiwan".

 

[Michael Mayben]

The counterbore in the front pump where the seal will reside must be clean and sterile.

Here ya see the replacement seal has been lightly pushed into the counterbore, the seal case has a slight chamfer on it to help guide into position in the counterbore.

 

[Michael Mayben]

While a special tool "driver" is nice to have to seat the seal, it's certainly not necessary.

If the pump is on the bench when replacing the seal, then I do use a driver. If the pump is installed as in this case, I simply tap around the perimeter gently using a brass hammer, until the seal is fully seated in the counterbore.

 

[Michael Mayben]

We're done!

Last step is to make certain the tranny penetrations are all completely sealed off so that no particulate or moisture can enter the case. Whether you are simply finishing it off and planning to re-install soon, or prepping for long term storage, the unit should be sealed to exclude any small animals or shopcrap. In this case I use a pvc vacuum cap to plug the vent, and duktape to seal the input side.

This tranny now goes outside to the degreaser and powerwashing station, then dried with the leaf blower, and loaded in the truck for delivery to t on May 30.

 

[MLS]

I just bought new seals from napa to fix my leaking shift shaft and the larger one doesn't look the same as the one I pulled out. I put it in anyway and it leaked right away, it doesn't have as much rubber on at as the old one. Where do you get the ones you use? Part #? Thanks

 

[Michael Mayben]

While I try and not deal with napa at all for anything, I have used the seal they supply in the past.

There are two different shift shaft seals used in these transmissions...I'm talkin' the shift shaft seal...not the "soft" throttle pressure control seal.

The one you need is the "thin" seal case item. It will measure 0.250" in thickness (1/4").

The seal you are trying to use will measure 3/8" in thickness and will not work in your transmission...but you already know that! That seal is for a much later variation of the base 727 model, the four speed unit with lockup.

There are many part numbers for that proper seal for your unit. But all the various numbers I use won't mean anything since they are proprietary to various wholesale suppliers I use and are not "standard" seal numbers.

If you insist upon using napa as a parts source for this item, then tell 'em ya need the shifter seal for a '78 dodge d100 pickup with 318 engine, auto transmission. And take your old part with ya for validation!

The best place to find this seal is your local independent transmission rebuild shop.

 

[MLS]

Thanks for the tip, napa had the same seal again even for the dodge. I got the right one from a local trans repair shop.

 

[Ike T]

Just want to post how helpful this thread is. I changed a leaking shifter seal and not-leaking throttle seal without issue in our '73 travelette.

Now, I get to drive the truck and see what else might be leaking. :d

 

[Michael Mayben]

just want to post how helpful this thread is. I changed a leaking shifter seal and not-leaking throttle seal without issue in our '73 travelette.

Now, I get to drive the truck and see what else might be leaking. :d

Big insider tip tim...if it's got liquid inside...it's leaking!

Next up..re-seal the valley cover, install new pcv grommet and then intake manifold gaskets! Replace the front crank seal (adding a repair sleeve if needed). Toss that gasket under the distributor mounting flange and replace with an "o" ring.

When ya make the left coast move, stop by here and we'll handle it all!

 

[Ike T]

when ya make the left coast move, stop by here and we'll handle it all!

I'll be happy to bring the jetta up to maybenville. I hope you like working on tdis.

I can't afford to drive the beast cross country again. Plus, I think it's too long to park anywhere in monterey.

 

[Michael Mayben]

I'll be happy to bring the jetta up to maybenville. I hope you like working on tdis.

I can't afford to drive the beast cross country again. Plus, I think it's too long to park anywhere in monterey.

You can leave the t'all parked at our place and come up on weekends and play with it?????

 

[Ike T]

you can leave the t'all parked at our place and come up on weekends and play with it?????

I'll need some supplemental income to afford those flights. You and I could stand on a street corner with a sign "here's a face only the bottom of a boot could love. $5 per step."

it will be cheaper to buy a Scout once there. This will probably be my last time living out west, so I'd like to see some backcountry once or twice before I move on.

 

[POPS]

here ya see the two seals we're dealing with.

The larger item is a conventional single lip seal with a steel case.

The smaller seal is for the throttle pressure control shaft and is a single lip seal also, but closely resembles a grommet and has no case...it's flexible.

Identify the lip on each seal...the lip must point down towards the fluid reservoir when installed!

Is there a source for the 'throttle pressure control shaft seal'? Chad had all the other parts for my reseal.

 

[Scoutboy74]

Well pops, since these are chrysler units for the most part, theoretically a fella should be able to go into the parts store of his choice, specify the item and at least be able to place an order for it, if not walk out with one in hand. These are dark days in the auto parts business. So in the absence of a local angle, you could try these guys:
https://www.wittrans.com/default.aspx

 

[IHC NUT]

Your description and pics are very helpful. I have identified that I have a leak coming from this area. I also think my pan gasket is leaking, so plan to do both repairs. I took off the access panel on the hump to have better access, but it is really tight there too.
I read where you can access this area through the pan also. Is that true? Doesn't seem like that would help since the seals go up, not down for removal. I also don't know whether to be leery of removing parts of the transmission to get there.

 

[Scoutboy74]

Always helps to know what the vehicle is to keep assumptions to a minimum. If it's a sii, then yes, access to the shaft seal is very restricted. If this is a fullsize pick-all, access is much more generous. It can be removed from above in an sii with an assortment of picks and hooks to jerk it out. It makes for an extremely tedious and cuss-laden endeavor. At one time, you could by a tool that was made specifically for removing these seals from above. It threaded down into the metal clad portion of the seal engaging the entire circumference. Then all you did was pull on that tool and the seal would pop right out with it. They were damn spendy for something the average person might only use once in their life, but worth every penny if still available. I think they're tough to come by these days.
Since you're planning on replacing the pan gasket too, that means the pan will be off and the fluid will be drained. Its a good time to throw on a fresh filter and verify band tension is within spec. With the pan removed, the valve body can then be removed, which would then allow you to pound the shaft seal out from below. This is much quicker and easier than trying to pry it out from above. The new seal would then get driven in from above. Now, vb removal has a few ticklish steps to it as well, so I can understand your trepidation, but having gone at this seal both ways, and having done several vb removals, its a no-brainer for me. If I have a failed seal to remove in a sii, I'm draining fluid, dropping pan and yanking vb to pop the seal out from below. But that's just me. You might try prying it out from above and land on just the right combination of picks and mini-pry tolls that you get the damn thing popped out in short order. That just hasn't been my experience.

 

[Richard]

Need help on this. I have a79 Traveler that I am putting back together. 345, 4bbl TQ, 727 w/D20 tc. Need to know:

After sitting on my garage floor for about 30 years, I am getting the 727 TF ready to put back in. Issue: I had the TF rebuilt about that long ago, and have NEVER used it. It's just been sitting. I have ordered, and received the necessary external seals to replace (thanks IHPARTS) and need to know about the internals:

are there any "internal" seals that can/could have dried out, or am I good to go? I guess this is my biggest issues as I don't wish to have it rebuilt again just to change out some internal seals (if there are any). As I mentioned, the tranny has never been run and has been sitting on my garage floor.

Thanks for the help.

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Scout2
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Yesterday at 10:46 AM

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• #2

May want to check the Shift shaft seals and the trans pan gasket

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Richard
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Today at 6:13 AM

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well, you are correct!
I did order the two items above from IHPARTS in a seal kit. My biggest concern is the "innards". Took off the D20 transfer case, all looks good inside, no rust at all. Took off the end snout (the part that the drive shaft pops into, same. I am changing out the shift seals and I have a reusable pan gasket from IHPARTS. My biggest concert is the "innards".

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[Richard]

Hey Scoutboy74:

could use your input. in the above thread, you are mentioning an internal "shaft seal" and/or "pump seal". Did I miss something and/or are these two seals actually inside the TF727? Need to know since I am getting this tranny ready to put in my 79 Traveler.

Thanks for the assistance.

 

[Scoutboy74]

The input shaft seal has a metal body with rubber sealing lips. The pump seal is a square cut rubber o-ring. Those two seals are generally replaced as part of a comprehensive rebuild process rather than in onesy or twosey fashion for whatever reason. I suppose it might be possible to source those seals individually rather than from a rebuild kit from a supplier such as WIT (Whatever It Takes) dot com. Rubber can deteriorate over time even when stored in a climate controlled atmosphere and not exposed to UV rays. I can't tell you with any certainty one way or another whether your seals have been compromised or not. You're on your own path of discovery there. Personally, I would install the trans, fluid up and run it to see what I had, but I also wouldn't be too put out if I discovered it was leaking and I had to drop it to replace a couple seals. That may not be the place you're in. The input shaft and pump is located at the front of the case directly behind the torque converter. The input shaft seal should be removed with a seal puller and the pump has to be pulled with a slide hammer puller. You start getting into it that far, you should have a service manual at the least or the Carl Munroe A727 book as reference to guide you along.

 

[Richard]

hey there, appreciate to response. Yes I did swap out the front seal, the rear yoke seal, and the two small pressure seals on the left side of tranny. Yup, I am going to thrown it and get it running.

Thanks, now onto another question, maybe should be on another thread but: the below attached snapshot is of the "internal" cable of an automatic trans shifter. I have four of them. got two of them apart and one of them is broken. I guess rust won. Anyway, I was trying to figure out how to get the broken one back together. I know IHPARTS sell the entire shifter, but don't need it, just the cable inside. It's a pretty simple design, just gotta figure out how to fix.

 

[Richard]

well,, got another question, if you don't mind. on the TF 727, where the trans. fluid filler tube goes into the body of the trans? just to the left of it, there is a threaded opening. What goes there? is it just a plug, or did I miss an electrical switch? the threads are the same as the engine oil switch that screws into the oil gallery of the engine block. appreciate the response, and thanks.