Rear Main

[RustyK5]

I'm a newbie oilburner and my Blazer is leaking some oil! I have read all that i can on replacing the rear main seal but I would like to hear from someone who has done this. Also which is better the rope seal or the newer neoprene gasket? Thanks.

[catmandoo]

they aren't too bad too change just a matter of getting the pan off which shouldn't be too bad in the blazer as for seal the neoprene is the only way to go the ropes are hell to put in if you don't have the special rope puller to pull it thru .my 82 sub with banks had a rear main leak and it really wasn't that bad considering i've seen lots worse anyway decided to change it one day and pulled the rear main cap off and there wasn't one in there top or bottom it must have had a rope and ate it ?fixed it and now the front started to leak.

[Eric Deslauriers]

Check to be sure your your anti-depression valve is functioning (that funky round metal canister with the one or two lines to the intake manifold). They're supposed to help generate a minor vaccuum in the oil pan, which helps keep the seals from leaking oil out.

As far as rear seal, I believe the new ones are Viton, no neoprene. Viton is the way to go.

[rumbler1]

Whether they're Viton or neoprene, the rear mains are not terribly bad to replace. Don't bother buying a cork gasket for the pan because it won't fit, just seal the pan with some good silicone when you're done.

[RustyK5]

Thanks for the info! I plan on diving in this weekend!

[HowieE]

Like to know what you find. When I opened my 87, which I had put a Banks Turbo on, I found less than 3/4 of an in. of the original rope seal up on top of the crank. I saw nothing when I dropped the cap and then passed a copper wire up over the crank and pushed out the small piece of seal that remained. I assume the seal had long since been blown out and the slinger grove on the crank had kept things from leaking until I installed the blower, then a leak appeared.
To slide the new upper half of the seal into place I loosened one cap forward of the rear cap allowing the crank to drop just enough to allow the seal to be pushed up and over the crank.

Good Luck

[ropinfool]

Well I just replaced my rear main seal, twice. And it still leaks. I was installing the upper, first one, had it 3/4 of the way in and I noticed a very thin strip of rubber coming off it. Sliced it right up. Went and bought another, $22 ouch, it went in better, prelubed it heavier. But it still leaks. I installed them according the directions on the package but noticed that one side of the seal had something like outer stamped on it, but this didn't point to the rear??? Did I install it wrong? Thanks. The bad luck continues. Truck is for sale by the way. John

[imported_]

I just replaced mine (on an engine stand so lots easier!) but that "outside" is supposed to go to the outside of the engine. I was a bit leery of it at first too because according to the drawing and the looks of the seal it appears at fist glance to go the other way, but the thinner lip goes to the outside as a dust seal and if you look closely you will see that the thicker lip is set a slightly smaller diameter than the dust lip = more pressure on the crank and towards the oil. and like you said on the first try make sure that you don't scrape the back edge on the seal going in to the block. remember that the seal is shaped exactly to the crank and is not bendable. lube it good and lay it right on the crank before rotating it in. I would suggest loosening ALL the main cap bolts so the crank will drop down so you can clear the edge of the block better. sorry for the long post.

[catmandoo]

every rear main seal i've seen comes with a little tab that you insert against the block to keep from stripping off the back of the seal.

[ropinfool]

Well it sounds like I installed it wrong, guess it'll have to sell with an oil leak. Thanks for the answers.
John