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91 GMC rear seal leak

Discussion in 'Chevy Trucks' started by bison1973, Dec 12, 2003.

  1. bison1973

    bison1973 Member
    Messages: 69

    I'm pretty sure the rear seal on my 1991 GMC 1/2 4x4 is leaking-lots of oil coming from that area. How is the seal replaced? Is it fairly easy-like through the oil pan? What has to be done? Thanks in advance.

  2. The Boss

    The Boss 2000 Club Member
    Messages: 2,099

    I've replaced tons of these for friends before on many different vehicles. 9 times out of 10, the motor has to be pulled because of the cross member on the frame. The oil pan has to come off and the rear main cap has to come off so the seal can be replaced. Make sure the new one is installed properly or it will leak. When I put it back together, I barely loosen all the main caps and then re-torque them to the proper ft. pounds and sequence. Also replace the oil pan gasket while your at it.:waving:
  3. nachoschevs

    nachoschevs Member
    Messages: 58

    I agree with The Boss. If you even tried to do it with the motor in, it probley would be harder in the end then pulling it out. Since you will have the oil pan off. I suggest if they make them for the newer years the one piece blue fel-pro pan gasket. They are very easy to put on and everyone that I know that has used them say they seal better then the four piece ones. I have used two and I did one with the motor in the truck. It was 100 times easer to put back on with the one piece.
  4. sonjaab

    sonjaab PlowSite.com Addict
    Messages: 1,425

    GUYS........On all the newer GM V-8s. There is NO 2 piece
    rope or neoprene seal anymore. The rear seal is a large
    O ring in a metal casing. ( Sorta like a hub grease seal).

    Just drop the trans. Use a seal puller. Take the old one
    out and slap a new one in !................geo

    But yet again it could be a broken oil pressure sender!
  5. 86burban

    86burban Senior Member
    from chicago
    Messages: 130

    I would pull the motor and do both the front and rear seals while your at it. redo the gaskets and the oil pump too. It doesnt hurt the wallet too bad and you will have your truck for a long time.

  6. The Boss

    The Boss 2000 Club Member
    Messages: 2,099

    I totally agree with you burban!:waving:
  7. Turfmower

    Turfmower Senior Member
    Messages: 376

    sonjaab is right it a 1 piece seal I changed mine when I did the clutch on one of my trucks.
  8. Stan

    Stan Senior Member
    Messages: 579

    Back a while ago my '94 k-blazer looked as if it had the same problem. Turned out to be bad "o" rings on the oil cooler connections that are located above the oil filter.