Diff fluids?

Discussion in 'Chevy C/K Truck Forum' started by wolfc70, Mar 9, 2010.

  1. wolfc70

    wolfc70 New Member

    My BIL and I just restored a 1987 Chevy 3/4 ton truck. It has 110k original miles and we are now ready to change the drivetrain fluids. The truck will only see 3000-5000 miles per year

    What do you recommend for the 14 bolt rear end? I was thinking of a synthetic gear oil, but my BIL has concerns about seals leaking. What have you had good luck with? Do you suggest the same for the front diff?

    The 4 speed manual calls for Dex II, so I was thinking any Dex III or equivalent should work ok.

    Transfer case. We think it is the NP 203, but not 100% sure. It has a weeping out put shaft seal, so that will get changed this spring. I think this runs ATF too.

    Any help will be appreciated!!!

  2. pmartin816

    pmartin816 Rockstar 4 Years 1000 Posts

    Welcome to the site.
  3. mmorgan1865

    mmorgan1865 Rockstar 4 Years 1000 Posts

    :sign0016: How about some pics on the restoration?
  4. wolfc70

    wolfc70 New Member

    Here are some pics.

    Attached Files:

  5. wolfc70

    wolfc70 New Member

    More pics. The truck has actually been done for awhile now, just working on all the little things to get it perfect. We took everything off but the cab and the drivetrain. Frame painted, everything rust proofed, and a 2" lift added. Everything is probably set up better than it came from the factory, panel gaps are nice and even.

    Attached Files:

    Last edited: Mar 9, 2010
  6. Chris Miller

    Chris Miller Rockstar 100 Posts

    Wow, that truck is beautiful! :D
    The NP203 actually takes 10w-40 motor oil.
    On the 14-bolt, I wouldn't bother with synthetic, unless you're going to be running at high speed. It does have a tendency to squeeze past the shaft seals and mess up the brakes.
    If the 4-speed calls for Dexron-II, yes, any Dexron-III will be fine. Just don't use Dexron-VI. It's compatible, but it's also a full synthetic, and might leak on you.
  7. Pete95Sierra

    Pete95Sierra Epic Member 5+ Years ROTM Winner 1000 Posts

    Here is what I do and havnt had problems

    -ATF in t-case.
    -conventional 75-90 gear oil in the diffs (Coastal from Auto Zone is cheap and works fine, I think 75-90 GL-5) with a limited slip additive if it has a limited slip. Its what I used in my 14 bolt without issue.
    -and run what the manual calls for in the trans, so Dex II.
  8. Elan

    Elan New Member

    awesome, im restoring an '85 pick up that is hte exact same package. nice truck! i have the same wheels too ;)
  9. 71k-10

    71k-10 New Member

    Very nice. I always enjoy seeing an old Chevy with a brand new life, it sounds like she is going to have a sweet life.

  10. dannys99

    dannys99 Rockstar

    Nice truck, about the fluids, not sure but I do know I blew out my rear end from listening to the guy at the auto parts store, so make sure to research for the best oil for each particular part number or component.

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