'94 Corvette Rear Main Seal

**pajeff02** · 05-13-2010, 06:19 PM

What the heck am I doing posting in the LT1 section of the Board?! Well... spent the last three evenings hanging out in the garage with TLS_Addict swapping out the rear main seal in his '94 Corvette. He has a beautiful, low mile vert that has been dropping oil from the bottom of the clutch cover. We looked the engine over and really could not locate any other possible source for the oil leak and dove into the project on Monday.

I have never wrenched on an LT1, so this was definitely a learning experience. In the Vette, the transmission is supported by an aluminum torque beam that bolts to the differential. The problem is, that after dropping the body X-brace and exhaust out of the way, we found that the torque beam cannot be removed from the vehicle. Per the service manual, you have to beat the beam as far rearward as you can -- until it touches the exhaust bracket at the differential.

Turns out this gives you just enought room to remove the transmission, but it is a very tight extraction. On installation, we unbolted the exhaust hanger bracket and beat the torque beam back another inch or so. This made the installation much simpler. Our only other serious fight was getting the clutch cover off the back of the engine. We tried popping the clutch fork to the side, but could not get the fork off of the throwout bearing. Unbolting the pivot ball cap and threading the ball into the case provided the needed clearance.

Everything else was pretty straight forward and the clutch and flywheel appeared to be in good shape. We cleaned everything off with a couple of cans of brake cleaner and then popped the old seal out. It is a rather thin seal with not much of a lip on it compared to the replacement. There was also oil collected at the bottom notch, so it did appear to be the culprit. The crank looked good with no grooves or wear marks, so we put a very light film of Ultra Copper gasket sealant in the seal bore, oiled up the new seal and tapped it home.

After the install, we took the car for a run last night -- first ride for me in a C4 in quite a while and might be my first ride ever in an LT1 car. It pulls hard and runs fantastic! This also has to be one of the nicest riding Corvettes of the C3 - C4 era that I have ever been in. TLS_Addict simply has an awesome car and really keeps it in nice shape. I enjoy projects like this and really appreciated the opportunity to lend a hand.

**5.0THIS** · 05-14-2010, 12:53 AM

LT1s often have oil leaks from the rear of the intake manifold, it's pretty common. I'm assuming you guys checked on that first

**pajeff02** · 05-14-2010, 03:19 AM

Absolutely. The car sat overnight in my garage before we started working on it and by the next day there was a significant oil puddle. We looked the top side over before we pulled anything apart. Although it had the usual oil stain (like you would see on an older oil pan or valve cover gasket) there was no where near enough oil there for what was running out the bottom of the cluch cover. We also looked at it again once we had everything off the back of the engine and it just appeared far to dry.

**TLS_Addict** · 05-17-2010, 03:28 PM

Hey Jeff! The car has not leaked a drop of oil. However I think there is still some residual oil in places where we didnt clean and on parts of the car (exhaust) it still puffs slightly and I can smell it but there is no leak anywhere to be found on the pavement.

Might have to throw an exhaust on it though.....it sounds just a tad on the wimpy side.

I like hte top on on this page Jeff, and it is a Magnaflow. lol

Says it needs welded on though so that might prove to be a little bit of an issue.

Thanks again Jeff, it was fun working on the car. We never really hit any snags other than that one bolt, and we wont say how we fixed it! It will stay our little secret.

**pajeff02** · 05-17-2010, 06:23 PM

Glad to hear that we stopped up the leak. That was really a fun project, even with the handful of setbacks. My garage door is always open for stuff like that.

I am just hooked on the sound of the Magnaflows -- both the T/A and the Vette have that nice deep rumble that just hollers under acceleration. Welding is not an issue -- there's a Hobart MIG welder tucked in the corner of the garage that you probably didn't see.

Don't forget the cruise in Thursday from 6-8 at Tractor Supply. I doubt the T/A will be ready, so we'll probably trip down with the Monte and the Vette.

**TLS_Addict** · 05-18-2010, 05:22 PM

Didnt see it but might have to try it out.....lol

Thanks again guy, I had a good time working on it even though we had a few setbacks. Maybe I will have to get the magnaflow cat back.