Tranny shaft seal

#1

I was hoping to install a new clutch and reassemble the drivetrain this weekend when I finally got around to examining the throwout bearing and input shaft. The bell housing is covered inside with a thick tar-like substance which is obviously either transmission oil or engine oil. I have previously removed and replaced the oil pan and stripped a couple of fasteners near the back of the pan which I have not yet had time to helicoil. I thought this might be the source of the oil, but the engine side of the bell housing looks relatively clean. I have not removed the flywheel yet to check behind it.

I’ve previously received advice here that the Getrags are notorious for input shaft bearing wear and most people just live with the racket. My input shaft can easily be rocked by hand over a couple of mm of travel. My question (finally) is does the loose input shaft eventually wear out the input shaft seal and how likely is it that this is the source of the leak? I’ll probably replace it in any event. A secondary question is is it worth replacing the input shaft bearing while the tranny is out. This seems pretty involved and would put a crimp in my schedule.

#2

If you have the transmission out of the car, I would really recommend replacing all the seals.

In addition if you do replace the seals, use Genuine BMW seals. They are more expensive, but trust me you don’t want to have to pull it back out to reseal it again later.

As a E30 specialty shop I have had the pleasure of resealing a couple transmissions from using aftermarket seals such as Elring. Just my suggestion from experience, I only use genuine BMW seals.

The common rattle you mention is not from the input shaft but instead from the ‘layshaft’ or ‘countershaft’ as it is called. Lovingly referred as the ‘Getrag Rattle’. This is from axial wear on the shims allowing the shaft to rock back and forth. Other then being a annoying rattle it is not much more. As a note you can access the front cover in the bellhousing and add a shim to eliminate the rattle or back and forth play.

In regards to the input shaft, some play is permissible. Keep in mind that when the transmission is installed the bellhousing is bolted solid the engine and the input shaft is held in alignment from the pilot bushing.

Hope that helps,
Robert

#3

Thanks Robert, that does help. I have been sticking to BMW seals whenever I make a replacement. What do you use in place of the factory sealant on the transmission input seal cover? The parts desk tells me they can no longer get the either the factory sealant or the recommended Loctite replacement due to some import regulation.

#4

Permatex Form-a-Gasket, or similar, will work.

#5

I use Permatex Hi-Tack sealant. I use it on almost everything, from holding gaskets in place, sealing gaskets, around the outside seal surfaces of seals, bolt threads, sensor threads, pipe threads, etc… Its great stuff actually.

It even works on sealing that front cover of the transmission :wink:

#6

Just got back from the first test day at NJMP. Aside from the car being extremely balanced with amazing brakes, I did have a pretty nasty fluid leak from the input shaft of the Trans.

I removed the trans. I’m assuming that the aluminum flange around the input shaft has to be removed to access some sort of a seal. Is this correct? Do I need any special tools for this? Thanks

Ray

#7

That is correct. The seal is under that piece.

#8

Last weekend I finished replacing the input shaft seal and I actually applied RTV sealant to the flange. I took it for a few laps around the block which added up to a few miles. I looked for leaks and found none. The car sat for a week. I just took it around the block again and put it on the trailer to get inspected tomorrow. I can see a drop hanging off of the bottom of the bell housing. It’s obvious that I didn’t fix the damn leak. Any ideas?

When I had everything apart the engine behind the flywheel was dry. The top of the Trans where the breather is was dry also. My first race in his car was supposed to be this weekend. Figures.

Ray

#9

You don’t want to see how much my tranny leaks. Just keep an eye on it and fill if needed. I check my tranny fluid level before each race weekend, and normally I don’t even lose enough to make a difference on the level in one weekend.

#10

The tranny that did not leak was an option on E30’s in the eitghties, but it was expensive and shouted German curse words so very few were made. Never seen one. I heard they live deep in the woods of Oregon with Sasquatch and the Tooth Fairy.

#11

Minor seepage from the transmission input shaft isn’t much of a problem. But I have seen a couple of cases where the leak was bad enough to wet the clutch. Nothing worked there except replacement of the input shaft and bearing.

#12

I went over to the shop where the car was getting inspected. Even the mechanic thought the input shaft seal was leaking. When I went under the car on the lift I noticed that the crap oil filter was leaking and flowing along the pan gasket to the Trans where it’s dripping. So in actuality I think the input shaft seal is fine. They still failed me for a moist output shaft and a naked positive terminal on the starter. Both will be easily fixed before this weekend. Anyone have any knowledge on changing an output seal?

Ray

#13

Output shaft seal…BTDT at least twice until I finally got it reasonably dry. The key seems to be using the proper sealant and following the directions in the Bentley to the letter. It’s been awhile since I did one, but I think the problem is more the output flange than the seal itself. Leakage occurs on the inside of the flange vs the seal surface, which has to do with sealant application.

My trans is still always ‘damp’ as it vomits lube out of the breather. ‘Full’ seems to be less than what the fill plug allows. I let the thing find it’s own happy place and just check it every so often to make sure it’s not gotten too low. I think this is a factory design to prevent floorpan rust.

#14

Seems legit. B)

#15

It is easy to add a vent tube up to the firewall and not loose any fluid.