Hi,

I recently did a search on this forum for input shaft leaks on M6 transmissions, particularly as they pertained to the use of synthetic transmission fluid and resulting ruined clutches but only found one post so I thought I would post this thread.

I have now ruined two clutches (before 70,000km) and thought last time that I had fixed every potential cause. I did the intake manifold fix with felpro gaskets and Ultracopper RTV, replaced the rear main seal as well as the rear main seal housing-to-block gasket in addition to replacing the oil pan gasket and RTVing that in place.

The problem returned and ruined my McLeod Single Disk clutch.

When I took the car apart to fix the clutch, there was no sign of oil running down the back of the block from above (my intake manifold fix was dry as a bone). When I put the car back together, I RTVed the bellhousing to the block and the tranny to the bellhousing to ensure that no oil could get in from above. The only thing I didn't RTV at the time was the junction between the starter and the inspection plate. I sort of thought there might be an oil leak along the side of the block that I did not see that was allowing oil down onto the starter and into the bellhousing.

At that time, I also replaced the transmission output shaft seal because it was leaking quite a bit, to the point where I would always park the car facing downhill, otherwise there would be drips on the driveway.

Now I have decided to stop guessing at it (like everyone ultimately does after they have wasted a lot of time and money chasing the problem without knowing fully what is wrong). So I got a Snap-On black light and U/V dye kit ($125, I think) and am going to check the engine oil first then the tranny fluid.

When I first pulled the transmission and clutch last summer after the clutch had been slipping for about a year (It is a summer use only car - and not much of the summer at that - given all the problems I have had), the inside of the bellhousing was caked with oil (or what I thought was oil). The clutch plate looked like someone had squeezed a half a tube of chassis grease on it. It was amazing I could get up the driveway, never mind accelerate with any speed. Also, the front of the transmission was covered in what I thought was oil but I was not sure where that oil (or tranny fluid) came from - at the time, I assumed it was coming from somewhere on the back or side of the engine and being flung around by the clutch/pressure plate once it found its way inside the bellhousing.

My theory for a while was that engine oil was leaking from between the head and block (or valve cover), down onto the starter and that the starter was spraying it around the inside of the bellhousing and ruining the clutch. Sounds pretty far fetched, I guess. Usually, as you know, the problem is actually quite simple.

My question is does the use of synthetic automatic tranny fluid in a T56 tranny often cause leaks like this? I used Mobil 1 synthetic ATF and I am now starting to think that the source of my leak and clutch problems is actually the synthetic tranny fluid and the input seal on the M6 tranny. The next question is do any of you think I can solve this problem by switching back to traditional tranny fluid (non-synthetic) and perhaps adding some tranny leak-stop (I know, those cocktails are frowned upon, but if it won't hurt and might help I would be willing to try it).

Next, is it worth it and is it hugely difficult to change the input shaft seal on the M6? Has anyone done it and will replacing the seal even fix the problem if it is actually related to the use of synthetic fluid? I tend to think that my leaks only started after the switch to synthetic tranny fluid, but I can't be sure.

I have also used synthetic Mobil 1 engine oil for a long time and seem to have a small weeping leak in the timing cover but am not sure if there is actually any meaningful or dangerous oil leak coming from the back of the engine anywhere. I guess the dye and black light will tell me.

In replaying what I saw when I pulled out the M6 tranny (and reading your old post, I now think that it may all be caused by a leak in the tranny input shaft seal - probably caused by synthetic fluid.

Please let me know any experience you have had in this regard and what you think about my situation.

Thanks for your patience in reading this novel.

 

Grant,

You obviously seem at wits end on this problem. I too have had a leaking valve cover on the starter side with no problems ending up on my clutch. The only problem was the input tranny seal.

The problem started with the tube that goes inside the throwout bearing on the clutch. This tube is glued to the input case cover of the tranny. This glued area leaked and was the cause of my first failure. If you do not understand what I am talking about, you will when you take out the tranny. It is very obvious.

Next what happened is allowing someone who said they have done many trannys to do the work. They put the seal in backwards. This allowed oil to leak by and again ruin my clutch. it was then that I decided to take apart my tranny and epoxy more permanently the glue area of this tube mentioned above. Then I double sealed the input shaft. No idea if double sealing will even make a difference, but I was damn sure not going to allow a simple seal force me to spend 8 hours under my car again!

I highly doubt it is the synth. doing anything. I use it on both my engine and tranny. As for the front cover leaking, so did mine because some doofus rolled over the water pump seal as he put it on the shaft. This is very easy to do and would not be suprised if this is your problem up front. Again, I had to do the real repair work.

If you have specific questions, let me know and I will do what I can to help.

Hope this helps.

Ben

 

When I redo this thing, am I ok to just remove the clutch and pressure plate, clean the flywheel and pressure plate thoroughly with brake cleaner and buy a new clutch disk, or will I have to replace pressure plate as well - because I expect it is all going to be pretty badly greased up.

What did you do when you had to replace the ruined clutch? Just the disk and a good clean-up of the other components? This thing is getting expensive enough as it is. I think I have about 6,000 KMs on it since I did the clutch last. I'd sorta like to burn it to the axles.

Thanks for the input.

 

I would just replace the disk and clean everything else up.

GL

 

I had a leak in the trans area. Did not ruin the clutch. Since I had the trans out, I had it rebuilt. The trans was OK. The rear main seal was leaking. Not alot but under boost the crankcase has some pressure and some oil would leak thru to the engine side of the flywheel. The oil stayed on that side and I never had a clutch failure. I replaced the rear main (used the GM type not Felpro) and the leak reoccured. I also tried Lucas oil stabilizer with by redline syn Eng oil, and, the leak stopped. I run redline syn in my M6 and it runs great. I would not know how engine oil gets to the trans/ clutch side???
----- 97 383 d1 M6