i do
always figured it was from the rear main seal aswell

 

What about output shaft seal?

 

here is a pic of the area where the leak is, the area circled in red at the bottom is where it is. must be a gasket between the seam where the cases meet.

 

My trans had a similar issue documented here: http://www.m5board.com/vbulletin/e39-m5-e52-z8-discussion/215864-slow-leak-tranny-drain-plug.html

I ordered a new plug and installed it with loctite to see if that was the source. Since then I haven't noticed any leaking, but also haven't driven much. Going to try and get under there this weekend to see if there is any dripping. Either way it doesn't leak enough to be an issue, but I'd still like it to be dry.

 

Nvm not same leak

 

Probably weepage from the joint. You can see the oil-filled part of the bellhousing below. I don't think the sealing faces in these trannies have gaskets, they just use Gasket Eliminator or similar.

 

I have an ongoing problem with this myself. It’s a very minor leak and tough to tell where it actually originates. I have a theory that it actually leaks from the bolt holes, but it’s hard to confirm. Since I’ve had a leak at both input and output seals in the past, you can basically rule that out for what the OP describes. You will know if you have a input seal leak if the transmission fluid leaks at the front of the bell housing through the inspection holes. For leaks at the output seal, the fluid will obviously leak at the back of the transmission and will typically drip on the exhaust when you drive. When I’ve had a output shaft seal leak, you could actually smell the transmission fluid burning on the exhaust. I’ve taken my transmission apart numerous times and can tell you there is no gasket or sealant to be found between the casing. It’s just metal to metal. When I was trying to resolve the leak mentioned in this thread, I used some sealant between the casing and I still get the leak. I have given up at this point and will deal with again when I get a chance. My next plan is to maybe use one of those LED UV flashlight leak kits. Also, I suspect there are many more with this problem, but just don’t know about since the underbody cover can easily disguise the leak. My leak is so minor, you would never know you had it unless you pulled the underbody cover.

John

 

I’ve taken my transmission apart numerous times and can tell you there is no gasket or sealant to be found between the casing. It’s just metal to metal.
John

Really? That explains why the joint faces look so clean in the photo above. Getrag must have a lot of confidence in their ability to m/c those faces dead flat and smooth.

Bolting the sections together with engineers blue on the faces would maybe show if the castings had distorted.

I've seen porosity in a casting cause hard-to-find weeping leaks. The dye and UV light would be a good way to detect that.

 

My next course of action:

 

was just under mine yesterday, I've got evidence of the same - no real wetness or leak, but signatures of a leak at some point... maybe it leaks when hot then dries up

it also looks like someone either used a test dye kit to find it, or some sort of goop to seal it up at some point - there are traces of a strange greenish sludge in some areas

as others have said - no real concern, never hits the ground (my covers are off this week) - I wouldn't fret it's not worth it

 

well my bolt hole fix didn't fix the leak. thought of another idea, the tranny must have a vent on top somewhere. wondering if the vent is partially blocked and allowing too much pressure to build up. does anyone know if the pic on the first page of this thread is a 420g trans from an m5? i cant tell with it split apart like that. looks like there is a vent on the upper part of the trans.

 

Yellow cap looks like the vent.

 

Yep, that's the cap. It should push up and down. Pull it straight up to replace.

John

 

does the cap have a hole in it or something to let pressure out?

 

I knew I should have taken a picture of that thing when I pulled mine out for inspection at one point. Anyway, if I remember correctly, it’s nothing more than a plastic piece that’s a little smaller in diameter than the transmission hole. It has a bell type of cap as depicted in Sailor’s picture that protects anything from going in the transmission. As far as your leak goes, I don’t think this is causing your problem. If your leak happens while the car is just sitting in the garage and not on, I can’t see how anything would leak upwards then out of this vent cap? I’ve thought the very same thing at one point. I still think your problem is related to the casing.

John

 

Just going by other vents but the cap could be there to protect a small filter of some sort. Not all vents have filters though, they are usually porous foam. The cap will be bigger than the tube and where it inserts into the tube be fins likely so that air can pass freely. Once you get the cap out you might want to check and see if there is something else hidden in the tube. Welcome back to E39 world.

 

Yes true but I think if it is plugged it would build pressure in the tranny and the weakest seal would leak? Do you remember anything under the cap?

 

I agree. From the way I understand it, the vent is used to relieve pressure on the seals while the transmission is moving. So, if it's clogged, it could potentially force a leak. In my case, I saw no obstruction and I actually put a screwdriver down the hole just to make sure. I'm going to try and poke around my car this weekend and I will try and pull that cap and take a picture just so you all can see that there is not much to it. I also have one of those video scopes and will try and shoot some video of the area.

John

 

im outside right now installing a set of rogue tranny mounts. i lowered the tranny and was able to get my hand up there and check the cap. the cap just spins around idk what secures it in place. i tried to pop it off but it didn't want to move and i did not want to break it.

 

That sounds normal to me. The cap just expands out inside the transmission. If you pull it straight up, it should come out with little force.

 

If it spins easy not likely plugged, unless there is a filter????? try blowing some compressed air into it or in the filler plug. That should make it clear if it is plugged.

 

update, i have finally been able to pinpoint where the leak is coming from but all my attempts to fix it to date have failed. its leaking from the hole where the dowel pin is on the drivers side of the tranny. i tried jb weld, indian head schellac, i even heated it up and filled the hole with pulmber's solder. it doesn't make any sense as there is really is no pressure in the gearbox so any of these fixes should have held. im done messing around, this weekend im taking it up to my friends shop to have him tig weld the hole closed!

 

nightkrawler,
Did you manage to fix your leak? I had to disassemble the transmission in order to fix jammed cruise control pin that got my tranny stuck on 3rd gear. I installed everything back last night and found the same leak this morning. I haven't started the car,so there is no pressure in tranny. I'm considering loosing the bolts and torquing them back in a crossed pattern, just being more precise in the right torque wich by TIS I found it to be 22Nm
I'm curious to know what did you endup doing.

Thank you!
Ves

 

Ves, thats the detent for the main selector shaft, right? I hear they fail under hard use - is that why yours failed? What mileage on the tranny?
Did you have to take the tranny apart because pieces had fallen inside?

 

no not yet, im going to have my friend weld tig weld the hole. it doesn't make any sense as there isn't really much if any pressure inside the gearbox, idk why that spot wont stop leaking. if i had the trans apart i would have knocked out that dowel pin and put a nut and bolt through the hole with a crush washer on both sides. you had the trans apart, is there any way the pin could possibly be knocked through with the trans already bolted together?

 

You need to punch out the dowels in order not to stress the housing while taking it apart. So yes, you can punch them out with the trans in the car. There is one more on the top part.
My guessing so far is that getrag didn't use any gasket in order to escape gasket failure since tranny is designed to be not serviceable. To manage that the surfaces needs to be extremely smooth and when assembling it in the factory would be used specific sequence and applied torque.
I'm curious why yours, if it haven't been dissembled, developed a leak.
In my case I may have scratched it or just haven't manage to torqued it properly which I will check tomorrow

 

nightkrawler,
I followed your idea and punched out the dowels and installed stainless steel bolts, nuts and washers. I will report with results tomorrow.

 

great! so you did this with the tranny in the car. was the pin hard to knock out? i was worried that if this is indeed possible the pin might be in there really tight and worried about cracking that flange area knocking it out. which way does the pin have to be knocked out, toward the front or the back? ie can it only come out one way?

 

I checked this morning, I didn't have anything dripping on the floor, yesterday morning I had a 2 inch puddle of mtf. So for now it looks good but I haven't run the car yet, I have it still up on jack stands. I will report back

 

knocked out the pins last night. fyi if you take a propane/map gas torch and heat the area up a bit they tap out quite easily. now my next question, what did you do about the front pin hole as the forward side of hole is not flat so a nut or bolt head doesn't sit flush against the case. i ground down the bolt head at an angle to try and get it to sit right.

 

I am sorry for the late response! I used a thick washer that I grounded down at an angle like you did with the bolt head. All this slowed down the leak but did not fixed it. I'm still getting a drop every 1-2 days. I will be loosing all the bolts and tighten them back on using more precise torque wrench so they all have equal force.
How is your situation? Did you manage to seal it?