Transmission Output Shaft Seal Leaking

[Stevedave]

Anyone have experience changing this out?

[Ultramaroon]

Does the driveshaft vibrate at all? Is the sleeve yoke scratched? Is the rear output shaft bearing worn? Why is the front pipe painted? Was the car driven over anything that could have bent the output shaft?


Get the idea? Many possibilities.

[Ultramaroon]

It's not terrible. I missed a fleck of sawdust trapped in the seal once when installing a replacement transmission. OMG, what a horrible mess that was.

[soundman98]

why does the transmission mount appear wet?

if i'm looking at the pictures correctly, the left side is the front of the car, correct?

usually a rear main seal would create a wet u-joint assembly. in this case, the transmission looks wet leading up to the rear, but the u-joint looks dry, indicating to me that the leak is ahead of the rear main seal.

normally vehicles are travelling down the road as they leak, so the leak is pushed backwards from the point of origin by the air flowing around everything. unless you drive backwards everywhere!

[Ultramaroon]

Originally Posted by soundman98

why does the transmission mount appear wet?

if i'm looking at the pictures correctly, the left side is the front of the car, correct?

usually a rear main seal would create a wet u-joint assembly. in this case, the transmission looks wet leading up to the rear, but the u-joint looks dry, indicating to me that the leak is ahead of the rear main seal.

normally vehicles are travelling down the road as they leak, so the leak is pushed backwards from the point of origin by the air flowing around everything. unless you drive backwards everywhere!

Oh, maybe the case vent valve is broken, or something else is loose. Gear selector shaft seal?

[soundman98]

Originally Posted by Stevedave

So possibly an oil leak from the engine working its way back? Something like a timing cover leak?

it shouldn't be a timing cover leak-- that would be at the very front of the motor-- any mechanic should be able to easily identify that, as the whole motor and trans would be wet.

i think ultra's thought of it being either a broken trans vent is on track, or possibly an over-filled trans. though in his picture, the neutral safety switch is on the same side as your pictures-- it could also be a failed switch allowing oil to pass by it.

Originally Posted by Stevedave

Are you thinking the leak is not transmission related? More specifically, nothing to do with the output shaft seal? In this case, would it be worth having a dye test done to see if the engine’s leaking oil?

very first thing to remove any further speculation, i would clean the transmission off of any current oil/wetness, and run a hand over hte suspected trouble spots feeling for lost/damaged/broken parts.

of course, it won't be fun getting under the car, and hosing it down with engine degreaser, but the first step in any leakage issue is to verify that the indications of a leak are a real and current problem, and not a past previously-corrected-but-not-cleaned problem, or even something as simple as a one-time over-fill event.

from the pictures provided, it just doesn't look like a rear main seal to me, unless you spend a majority of time driving the car backwards.

[Stevedave]

Originally Posted by Ultramaroon

Oh, maybe the case vent valve is broken, or something else is loose. Gear selector shaft seal?

From what I’ve read, it doesn’t sound like the case vent valve is removable. Is it possible that it’s serviceable and not removable? It’d be nice if replacing it is an option, and is an easy swap like the pressure relief valve on the differential.

If I’m going to be under the car, degreasing and cleaning everything up, might as well swap that out as a process of elimination. That is if it’s an inexpensive part and easy to get to.

[soundman98]

that could easily be residual oil dripping off. definitely clean first, and monitor.

[Ultramaroon]

Originally Posted by Stevedave

From what I’ve read, it doesn’t sound like the case vent valve is removable. Is it possible that it’s serviceable and not removable? It’d be nice if replacing it is an option, and is an easy swap like the pressure relief valve on the differential.

If I’m going to be under the car, degreasing and cleaning everything up, might as well swap that out as a process of elimination. That is if it’s an inexpensive part and easy to get to.

Safe money's on the gear selector seal. Nothing else really moves. I was just musing over other possible leaky points. I had to replace a failed check on a different beloved shitbox many years ago. I think soundman's right. Rear seal looks ok.

[soundman98]

Originally Posted by Stevedave

Ok. Since it’s been cleaned off twice, the seal replaced twice and doing this since I got the car in April, I’m thinking I’ll take it to the free follow up inspection on Wednesday. See what the shop has to say. I’ll ask to look at it while it’s on the lift and take some pics.

Would you still recommend not going forward with anything other than having the tech clean it all up?
Anything I should specifically mention to the tech while it’s there? I don’t want to be a jerk, but maybe asking if they’re cleaning everything up, not just around the seal.

It’s frustrating as my mechanic of 20+ years retired and I’m having a hard time finding a good shop in my area. A few people in the car community has said this shop is decent. So, I’d like to tread lightly.

i know the feeling. i try to keep to friends and siblings for work i can't perform, but with them getting busier with life, i have fewer places to turn to for work i can't do... it's really hard to find a good trustworthy shop anywhere.


this is my own talk of the 'reality check': the seal has been replaced twice, in less than 200k miles. which gives me major hesitancy to simply getting another one. that seal should be something that lasts the majority of the cars lifespan. it generally breaks down from age more than mileage, and we're not seeing others needing to replace it at all, with many cars in a similar mileage range. the fact that it's been replaced 2, and a recommended third time. something is off here.

it really comes down to 3 options.
A; it's not where the problem is, but appears to be due to the way the oil is flowing down the side of the transmission from driving the car.
B; the seal is a symptom, and the solution is a much more major shaft/transmission housing issue.
C; it really is a seal, and someone bumbleheaded the 2nd seal installation to cause a leak. it happens all the time, even in official factory-certified shops.

i don't like suggesting throwing parts at something like the transmission, because none of it is easy to access, and you're not performing the work yourself. if we were discussing a brake pad squeal, which just involves pulling a wheel and caliper to change, it would be much easier to recommend trying something different.

at this point, i'd really recommend cleaning as much of the transmission off as possible(brake cleaner is faster, or engine degreaser is the 'proper way'), then checking it within hours afterwards, and then follow up daily--whether the car is driven or not.

the earliest i would anticipate having any work performed would be 1 week later, assuming the leak continues and shows itself.

personally if were my car, i would jack up the car monday night, grab 5-6 cans of brake cleaner, some rags, and a face shield. i'd clean off as much as i could of the transmission. then tuesday morning and night i'd crawl back under and check it. same with wednesday morning--if the leak shows itself before that point, the appointment would be worth keeping. but if it doesn't, it'd be worth cancelling the appointment for a later date if/when the leak starts showing itself again, though i'd continue checking under the car for the rest of the week, and then slowly longer intervals until i'm confident that it really could've been a one-time overfill event--it does happen.

[Ultramaroon]

Don't throw parts at it. That's the most inefficient, least successful way to try to fix anything. Here are a couple pics of my original transmission. I think the stain on mine is only from the grease melted off of the shift lever retainer bushings, and shift lever pins.

[soundman98]

Originally Posted by Stevedave

There’s no signs of leaking from the output shaft seal or anywhere else on the transmission.

then the big question becomes "where are the driveway spots coming from?"

on one hand, i'm happy to hear you're working with a shop that's willing to not just throw money at the problem.

on the other, no sign of any leak only makes this more difficult...

[Ultramaroon]

Wait a minute. Why does the u-joint look clean in the first picture, and dripping with oil in the second?

[Ultramaroon]

Originally Posted by Stevedave

Lighting?

Got it. It did throw me.

Is that gap anything to be concerned about?

No. It's just to keep objects from jamming into the actual seal.