Replacing the rear transmission seal on my E30

[Steve L]

I have to replace the rear output seal on the Getrag transmission on my E30. It looks like I am going to have to remove the exhaust and front drive shaft to perform this job. Is that correct? About 5 years ago, I removed the exhaust and drive shaft. I really would rather not do it again, but expect that it will be necessary. Can someone confirm that?

[reelizmpro]

Maybe if you removed the heatshielding, you could remove the center support bolts and disconnect the driveshaft from the trans without completely removing it, then lower the trans brace and tilt the rear downward. I think you can probably do it without dropping the exhaust. I've pulled rear flanges from the JY but they cut the exhaust.

[Steve L]

Now that I have replaced the rear transmission seal in my car, allow me to tell you how it turned out. But first allow me to digress. Six years ago, I rebuilt much of my suspension and replaced a lot of parts in the underside of my 325is. But because I'm getting old and forgetful, I couldn't recall whether I could get to the back of my transmission without removing the exhaust system and drive shaft. My Bentley manual says that the exhaust system and drive shaft have to be removed. However, you can replace the rear transmission seal without removing either the exhaust or the drive shaft. That's good news. First of all, you need to remove the six bolts that hold the flex disc assembly to the output shaft yoke of the transmission. You can remove the heat shield between the drive shaft and exhaust without removing the exhaust. That gives you access to the intermediate bearing between the front and rear drive shaft. If you loosen the two bolts holding the bearing housing, you can slide the front drive shaft back on the splines of the rear shaft. You can then wiggle the flex disc assembly off of the rear of the transmission. I used wire to tie the drive shaft to the exhaust to get it out of the way.

You will probably have to make a special tool to hold the yoke while you honk on the 30 mm nut that holds the yoke to the output shaft. I used angle iron to drill holes and ran bolts thru the tool to the yoke. I would down load pictures of the tool, but the website says that the file is too big.

Getting the nut off requires a 30 mm deep 1/2" drive socket. I had to put oxy acetylene heat on the nut to get it loose. From that point on, the work becomes more easy. Also let me say that there were a number of different places that sold rear seals. The BMW seal cost $25, while the seal from Auto Zone cost $3.85. That seems like an easy choice, but I purchased both. The Auto Zone seal is called a differential seal, so it was for another application that could be used on the Getrag transmission. But when I compared the seals on the yoke, the Auto Zone cheap seal was much too tight. I installed the BMW seal. Less expensive isn't always better. This job is a bit of a pain, but very doable. Best Wishes to all of the home mechanics wishing to replace this seal. The biggest challenge was getting off the 30 mm nut. All of the rest was fairly easy.