Rear tranny seal.

[draccent]

For a while now, my transmission has been leaking slowly around the rear part. Its where the driveshaft bolts up to it. I'm starting to get the grease on my transmission mounts and am afraid of it eating them up. Not to mention the fact that losing oil in the tranny is typically a bad thing anyway. I have checked my Haynes manual for how to replace this thing, but can anyone shed some helpful light/tips on replacing this seal? And do I need to pull the transmission?

I actually would rather just pull it and do it along with the clutch if its better just to do all the seals at once. Thanks for the advice as always!

[ClutchSnappy]

nope, you don't need to drop the whole box.
Remove the exhaust, drive shaft, use a small hammer and drift punch to remove rear gearbox shaft nut retainer, put trans in gear, remove rear shaft retaining nut(you will need a deep socket), remove rear flange, remove old seal, pop new seal in gently making sure it goes is straight, lubricate id of new seal before putting the flange back in.
Reassemble!
Peace.

[draccent]

nope, you don't need to drop the whole box.
Remove the exhaust, drive shaft, use a small hammer and drift punch to remove rear gearbox shaft nut retainer, put trans in gear, remove rear shaft retaining nut(you will need a deep socket), remove rear flange, remove old seal, pop new seal in gently making sure it goes is straight, lubricate id of new seal before putting the flange back in.
Reassemble!
Peace.

Thanks! Exactly what I needed to know. Subscribed for weekend reference : )

[ddavidv]

The Bentley does a good job of step-by-step.
You will need a special narrow wall socket to get the rear shaft nut off. There is a socket for Ford diesel sensors of some sort that works, or you can grind one down to fit if you can't find one.
Follow the Bentley precisely and use loctite and sealant where and how they tell you. I replaced my seal TWICE before it finally quit leaking because I didn't follow the book (and, IIRC, went beyond what the book suggested in sealing the driveshaft flange). For some reason these seals can be problematic. Sometimes you can whip one in without a problem. The next time you'll have an endless stream of leakers.
It's not necessary to pull the trans to do this job at all, but it will be easier with it out of the car IMO.
Also check to see if the cap for the detent springs on the top of the trans is leaking. I've been told they can warp and leak over time. The replacements have a slightly different design and aren't real expensive.

[djb2]

The time consuming part of this job is removing the exhaust, although some say that you can just push it aside. The exhaust must be out of the way so that you can remove the heat shields so that you can lower the CSB (center support bearing) so that you can disconnect the driveshaft.

The only special tool is the socket -- see below. If you don't have an impact wrench you want to rig a bar up on the transmission output flange so that you can use a breaker bar.

You definitely will need heat to remove a output flange that was properly installed with permanent thread locking compound. I bent some pretty thick bars and bought a new impact wrench trying to unbolt one cold. It came only came off after heating for a few seconds with a MAPP torch.

When reinstalling the flange on output shaft you need to put the thread sealant on both the splines and threads. If you only put sealant on the threads you may get oil seeping past the splines. Clean with solvent just before putting on the sealant.

While you are there you really should replace the shift bushings and shift shaft seal.

Locktite 270 or Hylogrip or Curil K-2
High strength stud locker, 270 has been replaced by 2701 (alt #27040)


Driveshaft transmission output flange nut
Socket needed 30mm (1-3/16" = 30.16) deep thin-walled socket
Maximum diameter 1.521" or 38.6mm OD, although 39mm may work
Internal relief: minimum diameter of 15.5mm to 70mm deep

I first borrowed the "real" tool:
ST Tools BMW3025 socket is 39.04mm OD, 16mm deep flats, 66mm deep, $40

I didn't want to break it, so I gave up and bought my own inexpensive one:
Powerbuilt Tools Oil sender 1-3/16" 648445 $5.79 at partsamerica.com (local pick-up at Kragen, Advanced Auto, etc.)
37.85mm OD, 28.43mm wrench flats on end, 30.30mm flats
Internal relief: 19mm deep flats, 30mm ID to 67mm depth

[vdubpsu]

The time consuming part of this job is removing the exhaust, although some say that you can just push it aside. The exhaust must be out of the way so that you can remove the heat shields so that you can lower the CSB (center support bearing) so that you can disconnect the driveshaft.

The only special tool is the socket -- see below. If you don't have an impact wrench you want to rig a bar up on the transmission output flange so that you can use a breaker bar.

You definitely will need heat to remove a output flange that was properly installed with permanent thread locking compound. I bent some pretty thick bars and bought a new impact wrench trying to unbolt one cold. It came only came off after heating for a few seconds with a MAPP torch.

When reinstalling the flange on output shaft you need to put the thread sealant on both the splines and threads. If you only put sealant on the threads you may get oil seeping past the splines. Clean with solvent just before putting on the sealant.

While you are there you really should replace the shift bushings and shift shaft seal.

Locktite 270 or Hylogrip or Curil K-2
High strength stud locker, 270 has been replaced by 2701 (alt #27040)


Driveshaft transmission output flange nut
Socket needed 30mm (1-3/16" = 30.16) deep thin-walled socket
Maximum diameter 1.521" or 38.6mm OD, although 39mm may work
Internal relief: minimum diameter of 15.5mm to 70mm deep

I first borrowed the "real" tool:
ST Tools BMW3025 socket is 39.04mm OD, 16mm deep flats, 66mm deep, $40

I didn't want to break it, so I gave up and bought my own inexpensive one:
Powerbuilt Tools Oil sender 1-3/16" 648445 $5.79 at partsamerica.com (local pick-up at Kragen, Advanced Auto, etc.)
37.85mm OD, 28.43mm wrench flats on end, 30.30mm flats
Internal relief: 19mm deep flats, 30mm ID to 67mm depth

anyone know where to get this oil sender tool? I didnt see it at auto zone or pep boys and partsamerica is gone?

[djb2]

They raised the price when they changed the web site name:

http://shop.oreillyauto.com/ProductD...goryCode=3411T

The in-store price might be closer to the old $5-$6 price than the new $11 price.

There must have been some bad juju: they shut down partsamerica.com with no prior notice, and no forwarding URL. The oreillyauto.com site now has most of the partsamerica.com listings, but with a higher price. And they aren't associated with the east coast Advance Auto Parts stores, just Kragen/OReilly/Shucks.

[vdubpsu]

They raised the price when they changed the web site name:

http://shop.oreillyauto.com/ProductD...goryCode=3411T

The in-store price might be closer to the old $5-$6 price than the new $11 price.

There must have been some bad juju: they shut down partsamerica.com with no prior notice, and no forwarding URL. The oreillyauto.com site now has most of the partsamerica.com listings, but with a higher price. And they aren't associated with the east coast Advance Auto Parts stores, just Kragen/OReilly/Shucks.

can this be had locally?

[BlackBMWs]

You definitely will need heat to remove a output flange that was properly installed with permanent thread locking compound. I bent some pretty thick bars and bought a new impact wrench trying to unbolt one cold. It came only came off after heating for a few seconds with a MAPP torch.

I'll be swapping a Guibo and rear seal for my manual tranny for my 91 318ic this weekend. I have a few questions:

1. Will an impact wrench damage the internal gearing in the manual tranny? Should the tranny be in neutral or in a gear? (I'm thinking neutral)
2. So, if the output tranny flange is on firmly, where did you apply the heat? (Shown below is an auto tranny I pulled from my 325i for illustration purposes)
3. Also, once the flange is off, any tricks to removing the rear seal?

Oddly enough, I could not find the output tranny flange in RealOEM...





Thanks for any feedback!

[Wojtek79]

Good thread. I need to do this too.

[DmcL]

nope, you don't need to drop the whole box.
Remove the exhaust, drive shaft, use a small hammer and drift punch to remove rear gearbox shaft nut retainer, put trans in gear, remove rear shaft retaining nut(you will need a deep socket), remove rear flange, remove old seal, pop new seal in gently making sure it goes is straight, lubricate id of new seal before putting the flange back in.
Reassemble!
Peace.

this man speaks the truth.. this is how i did one on my last box before it died.

[IppoJ]

I'll be swapping a Guibo and rear seal for my manual tranny for my 91 318ic this weekend. I have a few questions:

1. Will an impact wrench damage the internal gearing in the manual tranny? Should the tranny be in neutral or in a gear? (I'm thinking neutral)
2. So, if the output tranny flange is on firmly, where did you apply the heat? (Shown below is an auto tranny I pulled from my 325i for illustration purposes)
3. Also, once the flange is off, any tricks to removing the rear seal?

Oddly enough, I could not find the output tranny flange in RealOEM...

I used an impact with the trans out of gear. I just held the flange so it didn't spin. I'm sure you could leave it in gear.

I didn't use heat on mine, I used a puller that I picked up at Autozone. Look for one like this:

Take your time tightening the bolts evenly and it will pull right off.

The only issue I had was finding something to properly seat the seal. I didn't have a socket large enough. So, look for something before you start the job.

Now, if I could get my selector shaft seal to not drool.

[djb2]

I continue to see the Powerbuilt brand socket in northern California Kragens for about $6-$7.

The same socket with a different brand is about double that in east coast chain parts stores. It's about the only thing that doesn't cost more in California.

If the output shaft nut was put in with the factory sealant, you won't get it off without heat. Not even with a good impact wrench. But the nut comes off readily if you heat the nut and output flange. Once the nut is off you can pull the still-warm output flange off with a gloved hand -- it's not pressed on.

[BlackBMWs]

Guys, thanks for all the feedback. While this procedure is fairly easy, I'll snap and post a few pics along the way.

At 140k, while I have items apart, I'll swap out the center driveshaft bearing as they are relatively inexpensive vs. the time to get stuff apart.

Cheers!

[draccent]

Any updates on this?

I haven't gotten around to doing the seal on my tranny yet because I determined the leak wasn't as bad as it seemed after a good clean.

Some good help to be found in this thread though.

[BlackBMWs]

I have the exhaust, drive train and shift linkage out. I can see the leak I have is the shift selector rod seal and not the rear tranny seal. I will change the selector rod seal but debating if I should change the rear tranny seal since it's not leaking.

Opinions if I should change the real tranny seal?

Thanks!

[Wojtek79]

Anyone come up with a step by step for this?

[SWISS]

nope, you don't need to drop the whole box.
Remove the exhaust, drive shaft, use a small hammer and drift punch to remove rear gearbox shaft nut retainer, put trans in gear, remove rear shaft retaining nut(you will need a deep socket), remove rear flange, remove old seal, pop new seal in gently making sure it goes is straight, lubricate id of new seal before putting the flange back in.
Reassemble!
Peace.

The time consuming part of this job is removing the exhaust, although some say that you can just push it aside. The exhaust must be out of the way so that you can remove the heat shields so that you can lower the CSB (center support bearing) so that you can disconnect the driveshaft.

The only special tool is the socket -- see below. If you don't have an impact wrench you want to rig a bar up on the transmission output flange so that you can use a breaker bar.

You definitely will need heat to remove a output flange that was properly installed with permanent thread locking compound. I bent some pretty thick bars and bought a new impact wrench trying to unbolt one cold. It came only came off after heating for a few seconds with a MAPP torch.

When reinstalling the flange on output shaft you need to put the thread sealant on both the splines and threads. If you only put sealant on the threads you may get oil seeping past the splines. Clean with solvent just before putting on the sealant.

While you are there you really should replace the shift bushings and shift shaft seal.

Locktite 270 or Hylogrip or Curil K-2
High strength stud locker, 270 has been replaced by 2701 (alt #27040)


Driveshaft transmission output flange nut
Socket needed 30mm (1-3/16" = 30.16) deep thin-walled socket
Maximum diameter 1.521" or 38.6mm OD, although 39mm may work
Internal relief: minimum diameter of 15.5mm to 70mm deep

I first borrowed the "real" tool:
ST Tools BMW3025 socket is 39.04mm OD, 16mm deep flats, 66mm deep, $40

I didn't want to break it, so I gave up and bought my own inexpensive one:
Powerbuilt Tools Oil sender 1-3/16" 648445 $5.79 at partsamerica.com (local pick-up at Kragen, Advanced Auto, etc.)
37.85mm OD, 28.43mm wrench flats on end, 30.30mm flats
Internal relief: 19mm deep flats, 30mm ID to 67mm depth

Anyone come up with a step by step for this?

Those guys did.

Good info, attacking the flex, CSB, shiftshaft seal and this on the wife's e46 this weekend.

[kmaxfield]

Check for a leak on the detent spring cover on the top rear of the trans. Is the leak higher up on the rear housing or clearly from the rear seal?

Also the shift selector rod seal could be leaking. Replaced mine last year, then a month ago noticed another leak. After removing driveshaft and heat shields noticed leak coming from upper rear trans housing. Turned out one of the detent cover bolts had loosened and there was little RTV on the cover. Resealed and replaced bolts. No more leaks.

[DmcL]

nope, you don't need to drop the whole box.
Remove the exhaust, drive shaft, use a small hammer and drift punch to remove rear gearbox shaft nut retainer, put trans in gear, remove rear shaft retaining nut(you will need a deep socket), remove rear flange, remove old seal, pop new seal in gently making sure it goes is straight, lubricate id of new seal before putting the flange back in.
Reassemble!
Peace.

what he said.. did one on my last box.. pity it took a dump about 1000 miles later tho lol

[325IXer]

When i did my tranny output seal last i first removed the lock ring with a set of needle nose pliers. Then removed the nut with a 30mm gear wrench deep socket ($10 at Advance Auto) on an impact gun.. I did not need a puller to remove output flange.. I simply tapped lightly and evenly around the output flange with a hammer to loosen it and it pulls right off.. If you have a puller feel free to use it but the hammer was closer to me at the time .. As kmaxfield said be sure to do the detent spring cover and the shift selector rod seal as well.. The shift seal has been the culprit on every BMW tranny i have ever pulled.. to remove the seal simply tap in with a screw driver at edge of one side of the seal and the bottom will kick out enough to pull out with a seal puller, pliers or screw driver.. careful not to scratch the sealing surface of tranny as it is very soft..

Also be sure to use a sealer on the output flange splines since i'm pretty sure oil will leak from it if you don't.. As djb2 posted Bentley recommends using Loctite 270 or Hylogrip or Curil K-2

Its not a hard job. If your exhaust has not been off recently i would say removing the will be the hardest part.. good luck! And if your still concerned about doing it get yourself a Bentley manual..

you do not need the pull the tranny to do the output shaft seal.. whether or not you should pull it to do the input shaft seal, clutch, pressure plate, throwout bearing, pilot bearing, resurface flywheel, slave cylinder and rear main is enitrely up to you.. all that will cost a lot more money not to mention pulling the tranny is a bit more involved.. requires a good 3 ft of extension a universal or two and a second person..

Some will say that if one is leaking the others aren't far behind.. while others will say if it ain't broke don't fix it..

[miklm]

Hate to bump an old thread, but this really helped me out, as we tried every socket in the shop and couldn't find one to fit.

The Powerbuilt socket mentioned above is available on Amazon for $8.81 - http://www.amazon.com/Powerbuilt-648.../dp/B002IO0PB0

Hope it does the trick. Thanks for the other tips and advice offered, I'll be sure to follow the Bentley exactly on this one to prevent any leaks. Trans is already out of the car so this is one of those "while we're there" jobs...

[motion]

+1 on the shift selector seal also before installing the rear flange check for fretting in the seal area polish if necessary. Just my .02

[87Cabrio89is]

I'm doing this myself right now and thought that I'd post a link to my flikr photo trail so that others venturing into this can see how I accomplished this task. I'll be creating my own "E30 build thread" soon, but have a question for now: I had to use a puller to pull the flange off after removing the nut. Yet the flange slipped in with little (perhaps none) resistance - do I have one of those "continuous leakers" in or is this the normal behavior? Obviously the Redline MTL that I put on the seal may have something to do with it, but I was expecting to need some effort.

http://www.flickr.com/photos/jtubert...7631898796649/