The Stovebolt Site Forums The Shop Area Engine Shop Rear Oil Seal

Well weve been talking about installing pan gaskets under a vehicle (already had my initiation into that realm of the spectrum, with a string of profanity and a yard littered with discarded gaskets and tubes of mangled blue-glue behind me some 20 years ago) but can anyone give any suggestions on replacing a rear crank seal while the engine is still in the vehicle?

Ive built several engines using the wick oil seal (on the engine stand), so am relatively familiar with the concept and even have a brand new shiny rear oil seal installation kit. Any of you folks played with these?

Ive also heard rumors for years that there is a Neoprene oil seal now available for the old chevys, anyone have knowledge of these?

Any thoughts, suggestions welcome......

There's a good how-to under the "Tech Tips" link above. These can be replaced without removing the engine or tranny. As far as the Neoprene seal, I think only '59 and later blocks are machined for this type of seal. If you do a search for "neoprene" you'll find lots of info.

Good luck and work safe - make sure the truck is sitting solidly on good quality jack stands.

Which engine do you have? A GMC or a Chevy? I have replaced a few 216-235-261 rope seals using the procedure described in the Tech Tips that Waldo53 recommended (follow the "Engine" sub-link), using both a home-made or a real "Sneaky Pete. I've also replaced rubber rear main seals in SBC engines with the same method.
If you have a Chevy, the 1929-57 Master Parts Manual shows only the rope rear main seal for all 40-57 sixes. However, Best Gasket shows the rubber seal for the 1956-62 235 and 261. For further confusion, a friend of mine bought a new 1954 261 short block from Chevrolet in the early seventies and it came with the rubber seal. I think (but do not know for sure) that the groove for the rubber seal is smaller than for the rope seal.
Chevs of the Forties shows the rope seal for 235 and 261s through 1958 and the rubber seal for 1956 and newer.

"CHEVROLET SEAL -REAR MAIN, RUBBER 2-PIECE
Seal-rear Main Rubber (2 pcs) designed for 56 and newer blocks, some earlier blocks may not seal correctly. 3835774 is original style rope seal."

Perhaps amore experienced Stovebolter or a tech person at Best Gasket could tell us the real details about the differences in the seal grooves. An Inliner with a GMC had success with the Best Gasket replacement rope seal.

Hoyt

There are many posts on this subject if one has the patience to use the search engine. I have done the one on my 216 and I pulled the transmission back to allow the crankshaft to drop some. On a 216, it is a good idea to adjust the main bearings at the same time. Too much clearance in the mains will cause a new seal to leak pretty quickly.