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Thread: Diff fluids?

  1. #1

    Default Diff fluids?

    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. #2


    Welcome to the site.

    1987 Chevy Suburban
    5.7 350 with Edelbrock Cam and Intake
    32x11.5x15 tires
    True Dual Series 40 Flowmaster exhaust
    Long Tube Headers

  3. #3
    Legend mmorgan1865's Avatar
    Join Date
    Feb 2010
    Port Orange, Florida


    How about some pics on the restoration?
    2010 Silverado Ext. Cab LTZ 2 WD 6 ft bed
    5.3L 6 speed w\ 3.08 rear end
    Navigation Package
    Westin lighted boards
    Undercover SE tonneau cover
    It's a start!

  4. #4


    Here are some pics.
    Attached Thumbnails Attached Thumbnails truckPicture 016.jpg   truckPicture 020.jpg   truckPicture 023.jpg   truckPicture 034.jpg   truckPicture 039.jpg  

  5. #5


    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 Thumbnails Attached Thumbnails truckPicture 043.jpg   truckPicture 044.jpg   truckPicture 075.jpg  
    Last edited by wolfc70; 03-09-2010 at 11:59 AM.

  6. #6


    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. #7


    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.
    95 GMC Sierra 2500
    3" Body Lift, 33" Goodyear MTR's
    5.7L 350 TBI Edelbrock SDT Exhaust, Flowtech Headers, K&N Intake
    Sold :(
    1999 Jeep Cherokee, 3" Rustys lift, 33" BFG MT's, locked, armored: Rolled :(
    2000 Jeep Grand Cherokee Limited. K&N Intake, Custom Kolak Exhaust

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  8. #8


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

  9. #9
    Jr. Apprentice 71k-10's Avatar
    Join Date
    Feb 2010
    Mapleton, Pa


    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. #10
    Sr. Apprentice dannys99's Avatar
    Join Date
    Mar 2010
    Northern California
    Blog Entries


    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.
    "If I were lie'n I'd be cry'n and I aint shed a tear"

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