Crankshaft rear seal didn't fix the oil leak

[QB93Z]

My problem started with an oil drip from the forward edge of the bell housing on my 1993 ZR-1 (102K miles). I guessed that it was oil leaking from the crankshaft rear seal.

Yesterday I (we) replaced the crankshaft rear seal, seal housing gasket and clutch. Thanks to all who helped.

I drove about fifty miles in the evening and parked it in the garage. This morning I have oil that dripped from the bell housing again.

My conclusion now is that the oil is coming from the transmission input shaft seal.

Anyone have any other ideas where the oil could come from?

Is replacing the transmission input shaft seal easy or will I have to rebuild the whole transmission to do it?

Thanks, Jim

[A26B]

Jim,
When you replaced the rear crank seal, where did you notice the oil leak "mess' in particular? If it's the rear seal, the mess should be confined to an area in the bellhousing between the flywheel & rear of the engine. A tranny seal would be confined to the rest of the bellhousing area, i.e. from the flywheel to the trans side of the bellhousing.

The trans input shaft seal should be accessible by removing the trans input shaft housing, with no further disassembly. Not a big job.....once you get the trans out. Any chance it might be overfilled? Should be level with the bottom of the fill plug.

[QB93Z]

Jerry, Thanks for the info. Here is the rear seal area immediately after the seal housing was removed, part of the old gasket is stuck at the top. The bolts holding the seal housing were basically finger tight so we thought we had found the source.

The inside of the bell housing was a mess all over. I couldn't determine an area that was the leak source. I cleaned it up so when I pull it again, I may get an indication.

Good to hear about the transmission input shaft seal being easy to replace. When I started this job I got a transmission rear seal from Advance Auto. When we pulled the transmission, it was obvious that they gave me the input shaft seal instead, so it was exchanged for a rear seal. I guess I should have kept it.

Jim

[Pete]

Jim the trans seal is easy of course after you remove the trans from the car.

I really haven't seen many leaky trans seals but then i haven't seen too many high mileage Z's.

Anyway the seal is easy to repalce no need for taking the trans apart.
It's in the input shaft housing the one with all the allen socket head screws take off the allen screws housing will come off the seal is in the housing.

The other issue is finding the seal, it only comes with the complete gasket set $200+.
I'm pretty sure if you take the seal to your local parts store it could be match up to something like an axle seal.

Gaskets for the the ZF are available from Flatout Gaskets,no seals.
I'm using Flatouts trans gaskets with no issues for over a year.
http://www.flatoutgroup.com/

Pete

[Pete]

Jim also make sure your PCV system is up to par.

If your running one PCV valve or are not 100% the motor will push oil out the seal, seen that on 2 LT5's.

Just a thought or something to look into to.

Pete

[QB93Z]

Originally Posted by Pete

Jim also make sure your PCV system is up to par.

If your running one PCV valve or are not 100% the motor will push oil out the seal, seen that on 2 LT5's.

Just a thought or something to look into to.

Pete

Thanks Pete. I will check it out.

[flyin ryan]

Sure does look like it was the rear main, doesn't it Jim? Strange... . Keep diggin'.

[tccrab]

Hmmm..
I was going to suggest the possibility of blow by from the oil box under the plenum dripping down the hole and then out onto the crank.
But I don't see enough crud around the block drain hole.

Rear main seal seems the most likely candidate.
Having a hard time seeing how the front seal on the input shaft of the ZF6 could cause a drip there. I would have thought that the flywheel/clutch/pressure plate would have blocked any tranny oil from reaching the rear main area.

TomC
"Crabs"

[A26B]

Jim,
Tom is correct about removing the secondary linkage shield to get the CCVH out for gasket replacement. I'm not one to recommend short cuts, but I would suggest that you consider leaving it in place & just tightening the bolts (13 if I remember right). You could snug down the corner bolts to start, then remove bolts, clean the oil off, apply a little thread lock & replace until all were done. I found the same problem on my '94 at 68K miles before the 415 build and did this procedure. No further leaks.

I fixed the oil pan leaks the same way & it worked fine.

Good luck Jim.

[QB93Z]

Thanks Tom. Thanks Jerry.

I had come to the same conclusion. I will try an incremental approach and see if tightening the bolts and grooming the PCV system will solve the problem.

Jim