Oil pan gasket, rear main seal question

[killian96ss]

What's up guys? My 05 ZR2 has an oil leak coming from either the rear part of the oil pan gasket or the rear main seal. I have never replaced either gasket or seal on a late model S10, so I'm wondering if either one can be replaced without pulling the engine. If it can be done, I'll go for it, but if not, I'll just wait until I pull the engine for a rebuild since it currently has 150k miles.

Steve

[HenryJ]

Might be worth dropping the front diff to do the job? If it is a rear main you would need to pull the transmission and transfercase. It is a one piece seal requiring removal of the flywheel ring gear IIRC.

Are you sure it is not the oil pressure sensor next to the distributor? We recently had a member fix one of those that was leaking.

[killian96ss]

It's hard to tell which gasket or seal is leaking since they are only an inch apart and inside the trans bellhousing. I have cleaned the area real good using the inspection hole for access and it looks to me like the oil is coming from the oil pan gasket. It is leaking a little bit around the whole perimeter of the oil pan and enough from the rear to leave a 4" puddle overnight which leads me to think it's just the oil pan gasket. The front diff isn't hard to take out so I might just try the oil pan gasket for now and keep my fingers crossed. If it is the rear main seal, I'll wait until I pull the motor or transmission for a rebuild which probably won't be long since I have 150k on the original engine and transmission, lol.

Steve

[HenryJ]

Sounds reasonable. Take the time to replace those axle seals while the diff is out. They may be due too?

[Horsehammerr]

It's hard to tell which gasket or seal is leaking since they are only an inch apart and inside the trans bellhousing. I have cleaned the area real good using the inspection hole for access and it looks to me like the oil is coming from the oil pan gasket. It is leaking a little bit around the whole perimeter of the oil pan and enough from the rear to leave a 4" puddle overnight which leads me to think it's just the oil pan gasket. The front diff isn't hard to take out so I might just try the oil pan gasket for now and keep my fingers crossed. If it is the rear main seal, I'll wait until I pull the motor or transmission for a rebuild which probably won't be long since I have 150k on the original engine and transmission, lol.

Steve

I'm sitting on 166,000 on my '02 CC and use,lose about 1/4 quart in 3,000 miles. Not concerned. Just remember to check oil every gasup. Been running Auto Cross lately, what a blast.

[paintballrocker]

i thought my rear main was leaking, turned out to be the pressure sensor leaking down the back of the block

[AVTekk]

Yep check the pressure sensor first, but honestly it all goes bad and you can do the oilpan with the motor in but youll need to pull the front differential. Heres a test, let the truck sit and idle for an hour and with a piece of cardboard under the oilpan. Then remove it and put a new piece and let it sit not running for an hour and compare the two spots. If theres a considerable amount more oil from it running, then something under pressure is the main leak which would be the rear main seal or sending unit. Of course if the oil is burning off the exhaust y-pipe then that test wont be as conclusive.