TC differences?

[76bluescout]

Hey all, my names chris, ive been lurking here for a cpl weeks now after I just picked up my first Scout. A 1976 4x4 Scout with a 345 and a automatic transmission.
To make a long story short I picked up the truck from a guy and he mentioned there was a "hole" in the origionel transmission that he had welded up right before I bought it. It drove fine for 1 1/2 hours of clearing snow with the plow right before I bought it so I didnt think much of it till I got it home and after 2 passes on the driveway reverse and drive were pretty much gone. ( ohhhh hun you know that truck that you didnt want me to buy....I might need to go buy a transmission) mmmhmmm that went over well
anyways the welding shop had decided to try to weld the casing, melted it in from what I can tell, and when they figured out that wouldnt work, they went and bought 2 lbs of jb weld and plastered it over the casing. Sooo I was off to the boneyard to find one and happened across another one that I was told was out of the same year Scout. I had done some reading up on mm's stickys ( good info btw ) and made sure they had the same bellhousing ect and that I wasnt getting something that wasnt from an IH.
Everything matched up so now im trying to put it up to the motor and the bellhousing is correct but the converter bolt holes that came with the new trans are closer to the center by what looks like from what I can tell about 1/2 - 3/4 of an inch compared to the holes on the flywheel. Did I screw up and grab an oddball trans? Or did they have different flywheels and converters on the smaller motors? Im at a loss here, any help would be appreciated. Thanks!

 

[Michael Mayben]

There are several different "diameter" torque converters used with all the variations of the 727 produced over the years for each oem. Then add in all the race car versions with their matching flx plates.

In the case of IH, three different diameter converters could have been used depending upon what the vehicle platform was, and what the total gvwr package might be when spec'd. Some oem flex plates were drilled for two of the three patterns also. Our new replacement flex plates will sometimes have only a single hole pattern, some have a dual pattern, depends upon who we source those from.

In the case of ihc stuff (not the amc engines or the Nissan diesel), there is only one single flex plate overall diameter/ring gear tooth count. Chrysler application torque converters have the starter ring gear welded to the case periphery, an IH pattern flex plate incorporates the starter ring gear, big difference!

As for the "hole" in the original transmission, that would depend upon where the hole is and what caused the hole. A cracked or holed bellhousing is easily welded by a pro that knows what they are doing as long as it does not involve a machined surface. In the old days, I welded up "holed" 727 bellhousings (when a flex plate would grenade) using oxy/acetylene and an aluminum brazing rod made for that purpose, the casing alloy used in those cases is extremely high quality stuff! Anyone that is a real welder and uses tig can also weld those up even when they are in pieces!

Some Scout II used a 10" converter (that is a "nominal" identification and not an accurate measurement) and some used an 11" nominal.

Fullsize stuff used both an 11" and a 12" converter. And a 12" can be used in a Scout II app if a suitable flex plate is used. The different diameter converters can have varying stall speeds designed in, thus the reason for various diameters, some gvwr vehicles need a lower stall unit, some use a higher stall setup...this also has to do with "emissions back when this stuff was new.

All the converters will interchange on the transmission side, but not all will match the bolt pattern on the flex plate. And all 727-pattern flex plates for oem apps use a four bolt-pattern converter, one of the bolt pads is slightly offset so that the balance of the converter/flex plate will be kept proper.

If the torque converter on the trans with the "hole" is servicable, why not simply use it since it matches the flex plate already?

I would never, ever use a torque converter from a donor, a boneyard, or someone's junkpile that I did not personally actually operate the transmission it came with. A torque converter is nothing but a trash pile internally and if the trans it came from toasted, then shit in that converter is going to take out any other trans it's put in front of.

A freshly rebuilt transmission always gets a freshly remanned torque converter!

 

[76bluescout]

Thanks for the reply michael! Yea I was thinking about that but with the way the transmission in the truck looked when the pan was dropped (chunks of metal, melted metel,ect not just the normal silt in the bottom of a pan) and judging the way there was no adjustment left at all in the band adjustments, I figured there was waay too much contamination that would have gotten into the origional tc to think about using it in the replacment. Now am I right in worrying about that? Or dose the filter catch that before it is ran through the tc? I wasnt too worried (at least before I read your post) about using the tc that came with the boneyard tranny, they actually put a metal tag on the housing to clamp the tc onto the input shaft so no sediments and water would get into it.
I also dropped the pan to put a new filter on right away and to adjust the bands and was happy to find that the bands needed no adjustment, the fluid was perfect color (it was used but with no burnt smell and no white/creamy color at all. And for the couple transmissions that I have replaced filters and fluid on I think this was one of the cleaner pans I have seen for sediments in the bottom of the pan. After seeing all that I was thinking the tc that came with that transmission was a better bet to use compared to the one that was in the truck when the transmission went. I up for ideas though, do you think im ok with the old tc? If so should I do anything to clean it out? Pull the plug and dump some clean fluid in to flush it out?
Incase I do need to get a new flexplate or a remanned tc what is used for a measurement to ensure that I get the right parts? Are the hole spread that bolt the tc to the flexplate measured? Or is it overall heights of the tc and flexplate?
Thanks again for the help!

 

[Michael Mayben]

Some torque converters have drain ports, many don't. The drain is only there for "draining" when doing transmission service (fluid exchange) and is not meant for any sort of flushing process. If you have a drainable converter, then by all means dump it,...but it's simply not possible to "flush" a converter in that manner.

I do not recommend a "converter flush" at any time. What that does is breaks loose tons of "normal" shit that is lodged in the nooks and crannies inside the converter where the stuff does no harm at all! If a converter is suspected to be contaminated, it should plainly be marked as such and set aside as a core for a remanufacturing process, that involves cutting it apart and replacing any damaged components and making the inside of it sterile before the two halves are welded back together.

Folks that "flush" a converter do so after a catastrophic transmission failure in an attempt to bring the package to life which is rarely successful since all the friction material inside is simply worn away! The worst offenders of this shit are the "quick service" outfits that simply wanna sell a useless service, what normally happens there is the transmission works fine before the flush, and fails soon after the flush. Of course, the quick service locations could care less and bear no responsibility in creating the issue to begin with.

In normal use, the filter does filter out any debris larger than the micron rating of the filter media. That debris is either held in the filter media or drops out into that "pile" of debris directly below the intake port on the valve body that is hidden by the filter. Most (but certainly not all) of the oem 727 apps had a magnet stuck to the inside of the pan to hold microscopic ferrous sluff, but the magnet does nothing as far as holding any organic friction material or non-ferrous sluff.

And everything I spit out here in this forum has to do with the old skool tf727, not any modern, computer-control throwaway transmissions that are "sealed" and can't even have the fluid level checked.

As for matching torque converters and flex plates...simply measure the center-to-center distance of the flex plate mount holes and match that to any IH-pattern converter!

The callout you see in some information regarding "diameter" is based upon the overall od of the converter case. And that diameter is not dead-on accurate but is a "nominal". One rebuilder's "10-1/2" converter is another builders "11" unit!

And to further muddy the torque converter waters, many of the remanufactured ihc-pattern converters were originally something used in a chrysler vehicle, an amc rig, maybe even a fork lift! When they were cut open for reman, they had the ring gears cut off and scrapped. Then when the cases were welded back together, they simply had no ring gear re-installed!

Measure the converter mounting pad bolt circle diameter, measure same on the flex plate and match 'em!

Based upon my experience with IH applications, a Scout II could have had a 10" or an 11" (nominal) converter depending upon which engine the trans was originally spec'd for, and fullsize IH vehicle (including a motorhome chassis) would have a 12" converter. There is no reference in the ihc technical information system that crosses oem converter part number with service part number, to diameter that I have ever discovered, though that information May well have been published in a service letter back in the day.

I work with one of the largest torque converter remanners in the u.s. Located up here. I've had this same discussion with them before, they have tons of data they use in referencing what goes with what that goes back into the late 40's, but they have nothing that references all the ihc stuff but that is not unusual in their business. That is why information like this is developed by those folks and kept "proprietary", it cost them money to develop it for their internal reference, they do not share that stuff except for their published catalog information available only to their customers which are wholesale accounts only.