ReallyWildStuff

Trans fluid was was more like "running out" after I had shut it all down...I'm wondering if a trans seal has failed / something is "wrong" - or if the setup on the run stand is simply tilted too far down in the rear to hold a full complement of trans fluid.

I have photos here:

https://flic.kr/s/aHskMx6pMb

I got my engine/trans combo started on the run stand a while ago - I brought it up to temperature and filled it with all required fluids (including trans fluid). I ended up adding 2 gallons (8 quarts) to the TH400/trans cooler system before the transmission dipstick showed it had enough fluid in it.

While I had it up to temperature/full of fluids I did confirm that the output shaft/yoke spun one direction in Drive, and the other direction in Reverse...but while I was not paying attention the output yoke did slide down and almost (but not entirely clear of) the tailhousing/output shaft.

I was able to stop everything in time and slide the yoke back up and all the way onto the output shaft (before it slipped all the way off), and seemingly without incident. The yoke still turned in gear after restarting after, and no fluid at all was leaking at that time.

Again, no fluid was leaking out the output shaft while the motor was running/immediately thereafter. I shut it all down and walked away.

Later I saw that some fluid was running out the output shaft and put a plastic catch can there. I came back to it later and saw the huge mess shown - with the catch can overflowing and fluid all over the floor. I don't know the capacity of the catch can but estimate it at "1.5 quarts" (not counting what's on the floor).

As you can see the fluid is not leaking from the "seal" around the output shaft, but is instead leaking from inside the union on the output shaft and the yoke.

What do you think? Did the fluid just run back downhill after I shut it down, or do you think there's something inside the transmission that's fouled up that's causing it to not hold onto all its fluid?

Thanks

droldsmorland

You likely rolled out the lip spring on the rear of the seal. Pull the seal and replace it with a HD truck TH400 seal. BDI has them. Google BDI (bearing dist inc.). Pack Vaseline behind the new seal to help retain the spring. Do not use grease. Also clean the bore out with brake cleaner then apply a thin coating of clear RTV around he new seals outer circumference. Wet the yoke with Vaseline or trans fluid before sliding it in. Use a seal driver or equivalent sized socket or pipe as a driver. Avoid warping the metal shell. Careful to not roll out the spring again.

mrolds69

I'm not a driveline guy, but maybe it's the wrong yoke? Not long enough to seal at the O ring? I think it should be a closed yoke with a small vent, not open like that one. I know there are many different yokes.........

ReallyWildStuff

Did this suspected "spring rolling" happen when the yoke slid OUT, or when I slid it back IN (do you think)?

That means the disembodied spring is somewhere still in-between the sealing areas, doesn't it?

ReallyWildStuff

I do not know the answer.

I do know that I was feeling pretty good about myself (engine running, trans turning) until I looked down at the output end of the trans and saw (what I now recall thinking looked like) a _long_ass_ yoke barely hanging on ("oh my gosh, what _is_ keeping this on?" answer=nothing), and that should have by all rights slipped all the way out by now.

RetroRanger

whats the time frame from ran and saw no leaks to saw leaks

maybe the converter drained back and the angle of your set-up contributed to the seal leaking?

droldsmorland

Yes and yes. It can happen goin in and out. Thats why you pack Vaseline on the spring. You still need to be careful.
But it is not your problem in this case.
I didnt open up the pictures at first. Sorry. Looks to me like the yoke is damaged. There should only be a little weep hole there. You shouldn't be able to see the splines and tail shaft end like that. That yoke has been slammed into the/a tail shaft hard enough to pop out the end. Get a new TH400 slip yoke. Dont use this one or you'll never be able to keep trans fluid from comin out.

oldcutlass

That looks like a rear end pinion yoke, note the ubolt holes.

ReallyWildStuff

I first noticed the leak was happening very soon after I shut it all off...perhaps that evening, or the next day.

A week went by (perhaps) before I noticed the "excessive" (multiple quarts) leaking. I admit to not paying attention to it in the interim.

ReallyWildStuff

Now we may be getting somewhere. I now realize that the driveshaft I had installed with this transmission is still complete and on the shelf with trans yoke still attached - and that I do not know the provenance of the yoke that's currently installed.

This yoke was found already slid onto the output shaft of the transmission when I unwrapped it from long term storage. Perhaps this yoke was temporarily installed to prevent excess fluid leakage? It does follow that one of my associates could have thrown this yoke into the parts mix at that time re: I had to remove the transmission from the wrecked car and didn't want fluid everywhere.

Would a rear-end yoke in fact have the correct diameter and spline count to slide erroneously onto a TH400 output shaft?

EDIT: It seems clear now that this is a Spicer-brand "End Yoke" , and not the "front slip yoke" that should be installed.

oldcutlass

Don't know never tried to install a rear end yoke in a trans.

ReallyWildStuff

Is it perhaps a 4-speed yoke Ive got in there now?

oldcutlass

The front ujoint uses clips on all 4 bearing cups, the rear ujoint is clipped to the driveshaft and is bolted to the rear end.

tru-blue 442

From the pics, that looks like a rear end yolk he's got. For reference here's a
couple of pics of a front yolk for a 4 speed Muncie and a 400 Turbo.

jcdynamic88

seems to me i've seen that style yoke on a gm pickup truck and the yoke is supposed to be bolted to the output shaft

droldsmorland

Missed the saddle bolt holes. dauh...Yes its likely a truck part and its likely for a pinion as thats where the pinion nut would live. Previous owner likely put it there in an attempt to prevent trans fluid from pouring out during trans port. Mystery solved Id say. Good work all.

tru-blue 442

66-67 r/e yoke .

jcdynamic88

not a pinion yoke,trans yoke bolted to the output shaft of trans. trucks with 2 piece driveshaft.

ReallyWildStuff

Thanks for all the help. It seems clear I have "the wrong yoke" or at the very least "a yoke that is missing parts"

Would this yoke I have on hand properly keep the trans oil inside the trans case if I additionally used the required (missing) pinion...bolt? nut? I understand this may be part of a two-piece driveshaft arrangement, but I have no reference for what those "missing" parts would look like.

If using these parts would solve the leaking: those same parts would prevent the yoke from slipping out of the tailshaft when running in a test environment, would it not?

OR: is use of a proper trans yoke the only way to correctly seal the oil inside the case?

I took some more pics and posted them here:

https://flic.kr/s/aHskMKtbJv

I took photos of a driveshaft with 400 yoke; I also took the "leaking yoke" out the back of the transmission and photographed that as well.

The transmission yoke/driveshaft was what I was running on the car when it last ran. The shaft is 3" long, maybe a little less. Closed in the back, as all good transmission yokes should be to prevent leaking.

The tailshaft on the trans is 4 inches long.

There was 1" of the "leaking yoke" still outside the trans case.

The "leaking yoke" is approximately 3" long overall.

Thanks again. Looking forward to discovering the path of least resistance re: securing the leak.

oldcutlass

You need to run the correct yoke for your driveshaft and transmission, that one is not it. One of the guys on here should have one. Place a parts wanted ad in the classifieds or you can get a new one at summit, jeggs, or a resto supplier.

ReallyWildStuff

Thank you oldcutlass - I understand that the yoke I have is not going to work under an actual automobile - indeed I already have a correct-length driveshaft, with the correct yoke, ready to go (as shown).

I was instead asking only about use on the run/test stand only. The requirement for this application is (at a minimum) NO LEAKS but it would also be really nice if the YOKE DIDN'T SLIP OUT of the output shaft/tailshaft when in gear.

Use of a "Correct" clips-on-bearings transmission yoke in this application will definitely solve the "NO LEAKS" requirement - but the yoke will still be in danger of slipping off/out in gear, as there's no driveshaft/located third member to keep the trans yoke stabbed up inside the trans.

What is the best choice for use on the test stand? Is it just not possible to both secure the oil as well as prevent the yoke from falling out with the same single piece of yoke hardware?

jcdynamic88

your output shaft doesn't have a threaded hole that would allow you to bolt the yoke in with so you can't use that yoke

mrolds69

The "right" yoke you have looks short to me. I know when I've bought tranny's in the past from boneyards, they would have a plastic plug like deal where the yoke inserted. There are different types of that plastic plug, one inserts in the tail. I think you could run the engine with the one in the tail, but I don't know how the plastic rubbing on the seal would be, and I don't know if it would fly off or not. What year is the trans?

oldcutlass

I think the centrifugal force may cause which ever yoke to try and spin out of there as they are only a slip fit.

ReallyWildStuff

Thank you for commenting on that issue. I relish the input.

At the time I put all this into an '84 Delta88 (c.2001) I did not have any reliable information re: "factory" driveshaft length for the final combination (TH400 "short tail" (right?) in B-Body platform with Buick 8.5 10-bolt posi from '78 Buick Electra).

I have been made aware that a TH-400 in a (much bigger) pre-1977 B-body would have almost certainly been a "long tail" (instead of the "short tail" I have). There were some 403-powered 1977 and later B-bodies with TH-400s from factory but I do not know for certain if they were long tail or short tail.

My 77 Pace Car has a TH-350 (so no good for comparison). The TH-400 was optional even with the W44 Pace Car package in that year.

All of the above is to say that "reliable (GM Factory) dimensions were not available", and I ended up trusting in both my hot rod associate as well as "Houston Driveshaft" re: determining both the correct overall length as well as the individual components that made up that length.

The squishy part always came down to:

the Goldilocks length of the driveshaft/yoke combo must allow for movement of the trans yoke in and out of the tailshaft housing due to rear end deflection - just enough so the yoke doesn't slip out of the transmission at maximum deflection, but not so much that the front of the yoke slams into the guts of the transmission when the rear end comes back to zero deflection.

In the photos I posted earlier:

The "leaking yoke" is 3.25"" (let's say - the correct measuring tools were not employed) and is fully inserted into the trans. I pushed it into the trans with my hands until it stopped. There was .75" "hanging out" of the trans, so there was 2.5" inserted. Right?

The trans yoke mounted to my driveshaft is 3", and (judging by the discoloration) had 1/2" hanging out of the trans at rest. That comes out to (the same) 2.5" inserted.

I did not have any problems that I can recollect with the driveshaft as-installed banging into the back of the transmission. That being said, I welcome input re: a better way to do it. I'm still good friends with my hot rod associate but Houston Driveshaft is out of business.

I put photos here:

https://flic.kr/s/aHskTh5Xri

The tag reads: 73-AA-37435.

The interwebs is thick with Chevy codes re: 400 ID information (also for Jeeps and other things) but I could not find a reliable source for "Oldsmobile". I welcome a link to that information.

My memory of the sale was "came from 1973 442" (Collonade-style A-body).

don71

The turbo 400 book by Ron Sessions list that transmission as being from a Cadillac and common in many models over several years, yours obviously in 1973.

ReallyWildStuff

Thank you. The stamped codes are clearly definitive as a Cadillac

Indeed now I see some references to Cadillac being manufacturer code "A". Still haven't found the Sessions info online - maybe a good plug for his book.

Should I be surprised that a 73 Cadillac used a "short tail" TH-400 instead of perhaps a "long tail" or even a "super long tail"?

droldsmorland

Dennys, Jegs, Summit, your local trans shop, local driveshaft house etc... should all be able to supply you with a brandy new th400 slip yoke.
If you're simply interested in preventing trans fluid from pouring out of the tail shaft until its installed in the car several vendors as well as trans shops offer a plastic plug that you simply slip into the tail shaft. Its real handy when installing the endine/trans combo to prevent red juice from pouring on the floor.
Even your local non big box house-of-china parts supply house should carry them.

Example:

https://www.summitracing.com/search/...ailshaft-plugs

don71

I hope you find that useful. I'm not a shill that tries to sell books, just trying to give the author credit. I'm an old guy, I buy books and not so much digital content.

There are many "tails" to the TH400.

ReallyWildStuff

I definitely did find it useful. Thank you. I did not mean to imply you were a "shill" or anything else.

If the info is in the book, then my own post is the "plug" for Mr. Sessions' book (aka I'm the Shill).

There is this (this guy thinks he's a hoot):

http://www.tpocr.com/cadillactc.html

Also this (although it doesn't reference Cadillac (or Olds):

http://www.teufert.net/trans/t-400.htm

Unclear how reliable any of this online information is.

I guess it's possible that the Division letter ("A" for Cadillac in this case) refers only to the "forward" parts of the transmission - and not to the tailshaft length per se. I have a hard time believing a 70-74 Fleetwood 60 Special used an "AA" T400 short-tail transmission like mine in any event.

I replaced my architect's 72 SDV transmission once (not the biggest Cadillac by far), even it had a "super long tail" T400.