Diff Seal Leak or Vent issue?
Thread Starter
Cruising
Joined: Nov 2006
Posts: 11
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From: Crab Island
Diff Seal Leak or Vent issue?
I watched the T4L diff seal video and ordered all the gaskets/nut/anaerobic sealant/surface prep he calls out. I’m now 2nd guessing that the seal is leaking and wondering if this looks more like it “vented” all over the back of the car… wondering if someone who’s had an issue?
Last edited by Stolen 98; May 22, 2024 at 03:45 PM.
Team Owner
Joined: Oct 1999
Posts: 31,976
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From: Guinness Its whats for B'fast JAWGA
CI 3-4-5-9 Veteran
It is hard to say without being under the car. The front of the transmission pan makes me question if the leak is starting before the diff but these cars are 20 years old and both maybe leaking and fluilds can travel all sort of places. The splatter on the exhaust and above the exhaust looks like the diff.
This guy a good series of videos IIRC on how to seal the diff.
This guy a good series of videos IIRC on how to seal the diff.
Last edited by 93Polo; May 3, 2024 at 04:01 PM.
Thread Starter
Cruising
Joined: Nov 2006
Posts: 11
Likes: 0
From: Crab Island
Thread Starter
Cruising
Joined: Nov 2006
Posts: 11
Likes: 0
From: Crab Island
It is hard to say without being under the car. The front of the transmission pan makes me question if the leak is starting before the diff but these cars are 20 years old and both maybe leaking and fluilds can travel all sort of places. The splatter on the exhaust and above the exhaust looks like the diff.
This guy a good series of videos IIRC on how to seal the diff.
https://www.youtube.com/watch?v=UoQk5rbt_KE
This guy a good series of videos IIRC on how to seal the diff.
https://www.youtube.com/watch?v=UoQk5rbt_KE
Team Owner
Joined: Oct 1999
Posts: 31,976
Likes: 487
From: Guinness Its whats for B'fast JAWGA
CI 3-4-5-9 Veteran
The more I look at your pics, the more I think something is going on with the transmission leaking.
I'm no mechanic, just spend to much time looking at this stuff as it cost less than paying someone I trust and I do ask mechanic friends about things when I get the chance.
Team Owner
Joined: Oct 1999
Posts: 31,976
Likes: 487
From: Guinness Its whats for B'fast JAWGA
CI 3-4-5-9 Veteran
It is an auto but agreed, low mileage cars come with their own set of problems. A Corvette friend had to replace many seals/gaskets on a low mileage C4 ZR1 and this took place 10-15 years ago. Dopping the trans isn't that bad of a job but I admit I am naive on filling the trans with fluid in an auto C5 just never owned one. I would be very tempted to replace the rear cover and rear main seal on the motor if I were dropping the trans. The seals are not that expensive and you're 85% of the way there.
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Thread Starter
Cruising
Joined: Nov 2006
Posts: 11
Likes: 0
From: Crab Island
I douched it down with 2.5 cans of brake cleaner and drove the car 5 miles…jacked back up and i can’t yet determine where the actual leak is. It’s definitely on the driver side…however I’m 90% certain that the axle seal isn’t leaking.
my question or confusion is coming from how a case leak could have thrown oil on the bottom of the car to the extent that it did?
my question or confusion is coming from how a case leak could have thrown oil on the bottom of the car to the extent that it did?
Burning Brakes
Joined: Feb 2022
Posts: 893
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From: NW Burbs of Chi-Town
2025 C5 of the Year Finalist - Modified
If its up high like that its from the axle seal and the axle/CV joint slinging it up there, or was on my car. anyway. I changed the left axle seal about 10k miles ago and I still have a bit of a very slight weep from the side cover. Someone here told me the new seal is an improved design? The leak seems to have slowed considerably, when I did the axle seal, I was all set to re-seal the cover with the required anaerobic sealer, but could not get the car high enough to get exhaust out. I need to find a friend with a lift. Changing the axle seal isn't that hard. GM seal and cover O-ring was $$$ on a Saturday morning from the stealer. I should have planned that better.
Burning Brakes
Joined: Jun 2007
Posts: 772
Likes: 213
From: Auburn Ohio
Diff Vent problem is worth looking into
Its “aThing” with these cars
If the diff vent is plugged it will not allow internal pressure to escape and the pressure
from expansion causes the gear lube to be forced out the side seals
if the vent is working properly,
the overflow can also vent out onto the driver side of the case
Look up the location. There are pics and discussion on this in other threads on this Plastic Fantastic forum
Save The Wave
USA-1
Its “aThing” with these cars
If the diff vent is plugged it will not allow internal pressure to escape and the pressure
from expansion causes the gear lube to be forced out the side seals
if the vent is working properly,
the overflow can also vent out onto the driver side of the case
Look up the location. There are pics and discussion on this in other threads on this Plastic Fantastic forum
Save The Wave
USA-1