Transfer Case Leak

Discussion in 'GM Powertrain' started by johnsonjf, Aug 17, 2010.

  1. johnsonjf

    johnsonjf New Member

    I have a 1999 K1500 with a 5.7, 4L60E and NP8, vehicle has 307K and runs great. The transfer case has been leaking from the PLUG,TRFER CASE ACC HOLE(RUBBER). I have removed the plug, cleaned it and the case well and replaced it but I used silicone sealant around the plug before I put it back in and then around the outside of the plug once it was in. It has set for about 24 hours and I will know later if it still leaks.

    Anybody else had issues with this? I know the case isn't low on fluid, I just put about 1.5 qts in and it wasn't coming out of the fill hole. Any recommendations would be welcome.

  2. triple-4x4

    triple-4x4 New Member

    In the same area you described, I seem to remember that people have a problem with the transfer case oil pump wearing through the rear half of the transfer case housing. Check for cracks or a hole in the rear case half which may cause the fluid to leak out.

    Look at this information:

    Hope this helps :money:
  3. Big75

    Big75 Rockstar 4 Years 500 Posts

    maybe try a fair amount of thread locker or teflon tape instead of silicone. If infact that is where the leak is coming from.
  4. johnsonjf

    johnsonjf New Member

    I've found a replacement transfer case, just a couple of questions. The information on my data plate indicates I have a NP8, the data tag on the transfer case shows 246GM. Are these the same transfer cases?

  5. johnsonjf

    johnsonjf New Member

    Ok, looks like finding a NP8 transfer case for my 99 GMC Suburban is more difficult and expensive than I thought. I guess I will be transplanting a manual transfer case into my vehicle. So any recommendations and suggestions would be appreciated. Below are the specs on my vehicle so you will know what I am working with. If anybody has a step by step procedure that would be extremely helpful.

    1999 K1500 GMC Suburban
    5.7 L gas
    4L60E transmission
    NP8 Electronic transfer case with 2 rocker switches on the dash

    My email address is

  6. Big75

    Big75 Rockstar 4 Years 500 Posts

    Sounds like overkill. is the case cracked? Or do you just have a leak from between two components?
  7. johnsonjf

    johnsonjf New Member

    Case already has 3 holes from the pump clip. The pump also makes noise and vibration when going down the highway at spped.

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