Is there an advantage to going either a one or two piece rear main seal?

A 1 piece is supposed to not leak. You usually also get with it a block that is roller cam ready.

The advantages of a 1-piece seal are less splits to leak from, better materials, and a smaller diameter meaning lesser surface speed on the lip, lesser friction, more life.

Disadvantage is either the trans or the engine has to come out to replace the seal. Takes some finesse to remove without scratching the crank and installing the seal straight into the bore.

Expertise has gotten to the point with 2-piece seals, they don't leak. All required is to remove the oil pan, starter, oil filter, trans inspection cover, oil pump, and rear main bearing cap, and remove replace seal. Clean the block & cap with lacquer thinner where they meet, run a 1/16 inch diameter bead of RTV or Gasgacinch, and mate the two together and assemble. You done.

Sometimes, better said than done. Always the possibility of ending up with a leaking seal again, and/or leaky oil pan gasket.

The advantages of a 1-piece seal are less splits to leak from, better materials, and a smaller diameter meaning lesser surface speed on the lip, lesser friction, more life.

Disadvantage is either the trans or the engine has to come out to replace the seal. Takes some finesse to remove without scratching the crank and installing the seal straight into the bore.



Everett is correct on removing the trans to replace the seal. But once the trans is out, there is a removable aluminum housing that the seal presses into. You can remove that housing and do the seal R & R on the bench, then reintall the housing, seal and all.

The one piece seal design uses a smaller bolt circle than the 2 piece design to attach the flywheel/flexplate, which some might argue sacrifices a little strength.

I believe GM makes an adapter to convert a one piece seal block for use with a 2 piece seal design crankshaft.

Another point to keep a two piece seal from leaking is to clock the split seals ends, say like upper seal tip at 2 0'clock and bottom at 8 0'clock, and apply a dab of Red rtv on the ends of the main cap and bolt up.

note that 85 and older engines are ALL 2 peice seal, no choice, and 86 and newer engines are ALL 1 peice seal, again no choice there.