GM-GMC: 93 GMC CK Suburban 4WD Rear Main Seal, gmc suburban, design engines

Question
Dear Mr. Jacobson,

I have a '93 CK series 5.7L efi GMC Suburban 4WD in need of a rear main seal replacement. My mechanic will only do the job if the seal is a one piece original seal, not a half moon or rope seal. Apparently the latter 2 involve much more labor, oil pan, engine removal etc.  Can you tell me which type of seal I've got?  VIN # 1GFK16K7PJ757473  Also since the truck is in excellent condition with 254,000 miles on it anything else that should be replaced or done when it's all apart? Front seal was done at around 200k miles.
 Thank you in advance for any response you send,
  J.W.Caldwell
  Union City, NJ

Answer
John,

The parts store data I have access to indicates that the seal should be a one-piece design.  A sleeve is also available, to renew the surface of the crankshaft, and it can only be used on the one-piece seal design engines.

Your mechanic is correct:  The two-piece or rope seal requires removal of the oil pan.  On some vehicles, that also requires removal of the engine.

About the only other item to check or replace is the front seal for the transmission.  While the transmission is removed, changing this seal is a good idea since almost the same amount of work is required to change it later if it starts leaking.