Rear main seals difficult?

[ackland3]

Allright so I've got a 85 k10 with a 700r4 and it seems i have the two piece rear main seal and i can't find any oil leaking anywhere else so does anyone know how to do a two piece? is it difficult? It's currently got the 305 til i can find a 350

[SkinnyG]

It's fairly straight forward, but involved.

Get a GOOD QUALITY rear main seal.  I used Felpro 2912.  I have heard the 2900 is good also.

I highly recommend the Felpro one-piece pan gasket.  I used OS34510T.

Once the pan is off, carefully remove the oil pump (note the oil pump shaft), and the rear main cap.

You should be able to poke one end of the main seal in the block and have it rotate around the the other side.

Use the crazy plastic piece to help slip the new seal in.  The wee tang stops the metal of the block from shredding the backside of the seal as it is installed.  Use it.

Some people offset the seal about 3/8" or so, so the gap does not match the block/cap join.  I have, and I have not.  I did not do so this time around, just to see.

Clean the mating surfaces of the block and the cap with brake clean or equivalent.

Use some sealant on the bottom of the main cap, to seal the mating surface.  Pay particular attention to the chamfer along the edges of the cap - oil can work it's way through there and leak.  I used Permatex Aviation Form-A-Gasket.  Do not put any sealant on the seal itself.  Google for pics on this.

Torque the main cap and oil pump bolt as per spec.

Straighten the pan flange with a block of wood and a hammer - make it as perfect as you can, they tend to distort and leak when over-tightened.

Put a dollop of Permatex Ultra Black or Ultra Blue in the corners of the main-cap-to-block, and the timing-cover-to-block.

Use the cool plastic clips that come with the one-piece pan gasket to hold it into place.  As you install the pan, make sure the wee "ear-tab-thingies" of the one-piece gasket fit in their spots at the main-cap-to-block corner.

Torque the pan to spec (evenly) with the new fasteners that come with the gasket.

Reassemble, refill, and enjoy no more oil dripping goodness.

[LTZ C20]

This is how we seal it now. Lol

[bd]

If you're not certain the rear main seal is leaking, remove the flexplate/converter cover and inspect for oil running down from the rear seal between the block and crankshaft flange.  If the block and face of the flange are dry, oil may be leaking from the back of the oil pan and dripping inside the cover making it appear to be the rear main seal.  Rarely the rear cam plug, located directly above the rear main seal, will seep oil.  A common scenario is oil leakage from the rear valley china wall at the back of the intake manifold.  Look closely until you are satisfied with what needs to be repaired.

To reseal the oil pan or replace the rear main seal refer to the 1984 Service Manual, beginning on page 644 for the oil pan and oil pump - page 648 for the rear main seal, augmented by the following narrative...

It's fairly straight forward, but involved.

Get a GOOD QUALITY rear main seal.  I used Felpro 2912.  I have heard the 2900 is good also.

I highly recommend the Felpro one-piece pan gasket.  I used OS34510T.

Once the pan is off, carefully remove the oil pump (note the oil pump shaft), and the rear main cap.

You should be able to poke one end of the main seal in the block and have it rotate around the the other side.

Use the crazy plastic piece to help slip the new seal in.  The wee tang stops the metal of the block from shredding the backside of the seal as it is installed.  Use it.

Some people offset the seal about 3/8" or so, so the gap does not match the block/cap join.  I have, and I have not.  I did not do so this time around, just to see.

Clean the mating surfaces of the block and the cap with brake clean or equivalent.

Use some sealant on the bottom of the main cap, to seal the mating surface.  Pay particular attention to the chamfer along the edges of the cap - oil can work it's way through there and leak.  I used Permatex Aviation Form-A-Gasket.  Do not put any sealant on the seal itself.  Google for pics on this.

Torque the main cap and oil pump bolt as per spec.

Straighten the pan flange with a block of wood and a hammer - make it as perfect as you can, they tend to distort and leak when over-tightened.

Put a dollop of Permatex Ultra Black or Ultra Blue in the corners of the main-cap-to-block, and the timing-cover-to-block.

Use the cool plastic clips that come with the one-piece pan gasket to hold it into place.  As you install the pan, make sure the wee "ear-tab-thingies" of the one-piece gasket fit in their spots at the main-cap-to-block corner.

Torque the pan to spec (evenly) with the new fasteners that come with the gasket.

Reassemble, refill, and enjoy no more oil dripping goodness.

...and refer to Re: Oil Pump? for annotated pics....

[78BIG-TEN]

Or oil pressure switch\sender could be leaking

[ackland3]

Okay thanks

[87ChevyR10]

Sounds like fun.... NOT. My seal is no bueno, so this same deal is in my near future. I feel your pain.