'96 M3 Trans Leak

[96M3]

Hello.

I have a '96 M3 which I just did a clutch job on. I also replaced main seal and trans. input seal. After I put it together I noticed a trans. fluid leak out the bottom of transmission. I pulled the trans. out again today and am planning on replacing input seal again. Figured I probably nicked it somehow when putting transmission in before. However, I noticed it looks like there is another seal behind this one (probably only accessible from inside trans. case). Wondering if this could also be leaking and if I should look into replacing this seal also before installing trans. again. Also using some different synthetic trans. fluid they recommended at a local shop called "Red Line". I looked into it more and I don't think this fluid is really recommended for use in manual transmissions - recommended for differentials. I am planning on draining fluid and using Swepco 201 instead. Could this also have played a part in the leak? Want to get this problem solved so I don't have to pull trans. out again (what a pain!). Thanks for your help!

[Jeron]

Don't use Swepco 201 it is not the correct viscosity and has the wrong additives. You need ATF weight oil preferably with syncro modifiers. Redline is a great product but expensive. I use Royal Purple SyncroMax, also expensive. You can use regular ATF, synthetic ATF or a dedicated MTF style of ATF.

Its only 2 qts so I would get the best fluid you can get locally, but only after you get the leak fixed.

As far as the leak, the most common leak is from the selector rod seal. Other possibilities are reverse and 1st sensors and the input and out put shaft seals. All leaks pool at the bottom so you need to clean it up and see exactly where it is coming from.

[96M3]

Thanks for reply.

I'm pretty sure leak is coming from input seal because fluid is leaking from inside bell housing (out the drain holes in the bottom) which would rule out selector rod seal and output shaft seal, right? Just find this kind of odd since I already replaced input seal and immediately it is leaking. Probably just got it cocked a little or something while installing. Anyway, I will look more closely at it today but will end up replacing input seal anyway since I already removed old one.

As for the fluid, I was just following recommendation in the "101 Projects" to use Swepco. The Redline fluid I have in there right now was recommended by a local store but looking more closely at the bottle, I noticed it says "Not recommended for use in most manual transmissions as it could cause gear clash due to extreme slipperiness of fluid". I'll do some more research into this today too.

Thanks again.

[Jeron]

Redline makes a lot of different fluids and they make one that is commonly used by M3'ers. It think it is called MT-90 but I'd have to look it up.

101 Projects is wrong about Swepco.

I agree, it sounds like the input seal.