4 speed leaking rear seal??

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Mopar92

Mopar92

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Made my first real miles today after a 360, 833, 8.75, and disc swap. I went to the muffler shop and got my exhaust done. Everything went pretty well. Have a slight leak around the oil filter adapter and bolt. I tightened it a little and crossed my fingers. It wasn’t real tight. I also noticed I’ve got a pretty good tailshaft seal leak. I did put a new tailshaft seal in it before I put it in the car. I got it from Brewers. I also put in a new Brewers yoke. I installed the seal with the hole at the top as well. It’s a pretty good leak. Shamefully I admit I didn’t have a seal driver to fit this seal. I used a brass drift and carefully put it in. Seemed to seat well although it buggered it a slight amount. It’s leaking from the boot part for sure. The boot is probably 1/16” or slightly less OFF the yoke. Almost giving me the impression I have the wrong seal. Is there another seal that is slightly larger and perhaps I got the wrong one ? This is a non overdrive trans. It does not have any vibrations or anything that would lead me to believe the bushing is shot. Thanks for any ideas or help.

Edit- the seal is probably .030” or so off the yoke. The boot does not touch the yoke.
 
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Mopar92 said:
The boot is probably 1/16” or slightly less on the yoke.
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Not sure what to make of this, but it doesn't sound good. What it does sound like is that your driveshaft is waaay too short.
There are two types of seals, one is like the front pump seal in an automatic. The second has a dust boot integrally mounted.
If in doubt, disconnect the rear, and push the shaft as far into the trans as it will go, then pull it back out about 1 inch, or just until the dust boot is free. If the U-joint caps are more than 1/4 inch from being seated in the rear yoke, then the shaft is too short.

On a different note, make sure the vent is breathing. If you like, you can pop that piece out of there, or pop the top off, and pressurize that box with shop air regulated to no more than 4psi. That will find/prove your leak right quick.
 
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It’s a brand new yoke and seal from Brewers. Perhaps I’ll call them Monday.
 
AJ/FormS said:
Not sure what to make of this, but it doesn't sound good. What it does sound like is that your driveshaft is waaay too short.
If in doubt, disconnect the rear, and push the shaft as far into the trans as it will go, or until some part of the front yoke crashes into the the dust boot; then pull it back out 1 inch. If the U-joint caps are more than 1/4 inch from being seated in the rear yoke, then the shaft is too short.
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I edited auto correct. The driveshaft is sticking 3/4” out of the trans from being bottomed out. The boot part of the seal does not make contact with the yoke. I know the boot isn’t technically a seal... but it’s oozing pretty good from there.
 
Well before you call, then prove you didn't dislodge the gator-spring with your tapping. If you did, then you can bend a coat-hanger wire and reinstall it without removing it. IF you replace that seal, put some grease on that spring to prevent that. I have, in the past, successfully removed that rear seal without damaging it, but I fabbed up a curved spoon to do it. Once out, you can fit it to the yoke and see what's going on.If you damaged the seal during the install, it will be leaking from the outside perimeter. If it leaks from inside the boot and comes out the weephole at the top,or from the yoke-interface, then IDK; it looks like a mismatch of parts.

Some older style of yokes had a weephole in an expansion-plug, installed on the end of the front yoke,altho I think that was GMs.
And as always, make sure you didn't overfill it; there shouldn't be any oil back there other than splash....unless....... you can leave, wheels-up!,lol.
 
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Yeah I’m not sure. I looked at the invoice and checked their website and it seems to line up with what they sell. Should the boot ride the yoke a little bit ? I looked at my buddies Hemi GTX and it sure looks like the boot has made whiteness marks on the yoke. The seal
Isn’t banged up I just didn’t use a driver but I took a lot of time keeping it square too. I appreciate the advice. Thanks.
 
Mopar92 said:
Should the boot ride the yoke a little bit ?
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I don't understand;
the yoke should extend into the trans some 5 inches, so yes the boot will ride the yoke, and should be a light friction fit to it, always keeping the yoke clean for about 3/4 inch behind it, as the moving rear suspension pumps the D/S back and forth thru the boot.

If you kept her square, and didn't pound on it, then the seal carrier will be fine.

However it occurs to me that you might not know that there are two sizes of seals and yokes.One for the 727 sized yoke and another for the 904 sized yokes.
I didn't think you could mix them up but I think this is what your questions are steering me towards.
The A-body transmissions come in two flavors one with the 904 sized M/S and the other with the larger 727 sized M/S. So if you installed the 727 sized seal, on the 904 size yoke, then the boot would NOT ride on the yoke, and there would be a bigb space for the oil to pour out on take off, between the yoke and the large seal.
So?
The small-shaft A833 is known as the slantybox. The large-shaft is what you should have for a 340/360.AFAIK the shafts interchange, except the OD box is also a small-shaft box. I have swapped several examples of all the shafts around, as I needed them.

When you said the boot was OFF the yoke, I thought off the back unmachined part. I didn't catch that you mighta meant off the sealing surface, So
Sorry for my thick-headedness.
 
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I have a lot of driveshaft In the trans. I'm saying that the boot seal is a credit card thickness off the yoke surface. In other words the boot part of the seal hovers over the yoke. Well I bought it from Brewers over the phone. I'd sure hope they didn't sell me a 904 seal. I'll call them Monday and see. Seeing it's his yoke and seal. Thanks.
 
Mopar92 said:
I have a lot of driveshaft In the trans. I'm saying that the boot seal is a credit card thickness off the yoke surface. In other words the boot part of the seal hovers over the yoke. Well I bought it from Brewers over the phone. I'd sure hope they didn't sell me a 904 seal. I'll call them Monday and see. Seeing it's his yoke and seal. Thanks.
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No I think you have a 904 sized yoke in a 727 sized seal. Try pushing the yoke up as high as it goes, then pulling it down as far as it goes. The bushing clearance is very small with new parts,perhaps .030
You can't put a 727 yoke thru a 904 seal, but you can sure slide a 904 yoke thru a 727 seal. I don't recall the sizes, but I'd guess the difference is about 1/8th or more, and that correlates nicely with your 1/16 clearance on each side.
 
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What about the tail shaft bushing and fit to the yoke? The Seal holds back drops. The boot just keeps the grime away from the seal.
 
1969383S said:
What about the tail shaft bushing and fit to the yoke? The Seal holds back drops. The boot just keeps the grime away from the seal.
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Seems to fit pretty tight. About what I've always felt. I'll pull the driveshaft and see if I've knocked the tensioner spring out or something weird.
 
Mopar92 said:
Seems to fit pretty tight. About what I've always felt. I'll pull the driveshaft and see if I've knocked the tensioner spring out or something weird.
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Just for giggles is the fill level correct? If dope is running out it is more than just a seal issue IMO. Seals only stop minor fluid, the bushing holds back most of it.
 
It isn't overfilled. Had a new bushing installed when it was rebuilt when I bought it. Looked new as well.
 
The boot should be rubbing on the yoke, no clearance at all. How many splines on your otput shaft? That will tell u what trans u have, and what parts u need
 
I called Brewers and gave him the VIN. I counted the splines but I can't recall. Bought this stuff in November. They are nice enough. I'll call Monday.
 
Last 2 cents is there is a mismatch somewhere in the yoke or have you checked the vent for obstructions causing undo pressure build-up?
 
The vin does not tell exactly what trans the vehicle has, that would be the fender tag. Or does the trans have the same last 8 of the vin stamped on it. And u said it was a swap?
 
Yoke diameters

904 = 1.558
727= 1.6875
According to Denny's driveshaft. Hmmmmm that's about the difference I told you guys it was.
 
Marcohotrod said:
The vin does not tell exactly what trans the vehicle has, that would be the fender tag. Or does the trans have the same last 8 of the vin stamped on it. And u said it was a swap?
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It’s been 5 months but I just read all the numbers to Wayne. He told me what I had.
 
I leveled the car and removed the fill plug. Some fluid came out. Not much. Maybe 3-4 oz. it was fairly foamy and it’s new Synchromesh lube. Not sure what that’s about. We’ll see if that stops the leak. It was a touch over full.
 
Mopar92 said:
I leveled the car and removed the fill plug. Some fluid came out. Not much. Maybe 3-4 oz. it was fairly foamy and it’s new Synchromesh lube. Not sure what that’s about. We’ll see if that stops the leak. It was a touch over full.
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Post back and let us know. Doubt you messed up the seal, cause all you need to do is lightly tap it in and a special seal driver Is not needed with care.

Don’t forget to be sure the vent is clear. Post a pic of the lube you put in as well.
 
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Yeah I will post up. I took out 6oz and let’s see. The foam to me indicated an overfill personally. I know on certain road race transaxles if you over fill one it will make pancake batter out of any oil. Synthetic or not.
 
Edited my last post, review and post the lube type. How much leaked out as well add that to to 6 once’s.
 
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