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  1. #1

    Default Fluids on a 99 GMC SIERRA Z71 NBS

    I am fixing to change the rear, front differentials and the transfer case. I know someone has told me on here but I cannot find it and the PO still has not found the owners manual. But can y'all tell me what I need in these. I like ROYAL PURPLE, tried and proven in my HARLEY DAVIDSON... So I would really like to use that...... But I need to know weights .... And how much so I can buy enough of what I need. Truck has 250k, so I don't think they have been changed, maybe the transfer case but not sure. PIECE OF MIND !!!!!!

    - - - Updated - - -

    I know someone told me this info on another post but I cannot find it and would really like to change the fluids today but don't want to put anything in that I'm not suppose to

  2. #2
    Legend

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    the amsoil web site has all this info . look here ; http://www.amsoil.com/mygarage/vehic...500%20PICKUP+T

    now you must know what rear diff you have so be sure to check the glove box code list.

    my 2000 silverado uses 75-90 wt synthetic gear oil rear locking diff eaton. the front diff uses 80-90 wt GL5 gear oil. the transfercase uses trac II transfercase fluid. transmission I have used mobil synthetic transmission fluid since 2001. this is pre dexronVI which is now the GM approved fluid.

    I did not change to the dexron VI as the fluid I have been using will not have the damaging effects of the defective DEXRON III that GM used to recommend in their fleet of vehicles.

  3. #3

    Default

    Quote Originally Posted by j cat View Post
    the amsoil web site has all this info . look here ; http://www.amsoil.com/mygarage/vehic...500%20PICKUP+T

    now you must know what rear diff you have so be sure to check the glove box code list.

    my 2000 silverado uses 75-90 wt synthetic gear oil rear locking diff eaton. the front diff uses 80-90 wt GL5 gear oil. the transfercase uses trac II transfercase fluid. transmission I have used mobil synthetic transmission fluid since 2001. this is pre dexronVI which is now the GM approved fluid.

    I did not change to the dexron VI as the fluid I have been using will not have the damaging effects of the defective DEXRON III that GM used to recommend in their fleet of vehicles.
    @j cat are you running a friction modifier in your rear diff? if so which one? I am running the amsoil 75-90 in my diff, but get conflicting reports about using a modifier.

    1995 Silverado 4x4
    6" BDS Suspension Lift-3" Body Lift-Add A Leaf in rear -Trailmaster SSV Shocks-Duel Steering Stabilizer Kit -AirAid Cold air intake-
    4.56 Gears with Detroit Auburn Locker-Pro-Comp Traction Bars with duel shocks-Aluminum Skid Plate Kit-38.5" x 16.5" Mickey Thompson Baja Claws-Constant Dropping fuel gauge

    2005 Yukon XL Jet Power Programmer, Bilstein Shocks, Bilstein rear springs, Helwig Anti-sway bars, EGR Window Visors, EGR Hood Shield, Denali Headlights, Headlight harness upgrade, GE NightHawk Bulbs, White Night Rear lighting system, Russell Braided SS brake lines, PowerStop Brake pads, PowerStop cross drilled and Slotted Rotors, http://www.gmtruckclub.com/forum/sho...5-GMC-Yukon-XL
    2002 Silverado ext cab 2wd (Sold)
    2003 Yukon XL (Totaled)

  4. #4
    Legend

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    Quote Originally Posted by Pikey View Post
    @j cat are you running a friction modifier in your rear diff? if so which one? I am running the amsoil 75-90 in my diff, but get conflicting reports about using a modifier.
    The friction modifier is used in my full time limited slip 1996 impala. this requires the friction modifier to reduce chatter when making turns.

    the truck with the eaton locker is just 75-90 wt synthetic.. modifier will mess it up ..these differentials are made quite different and the operation is very much not the same.

    with the truck the rear diff is not with both wheels providing traction all the time..only when one wheel rotates more than the other will the rear wheels lock together as one axle..

    with the impala the rear diff is always working as one axle . both wheels provide traction all the time..the problem with the impala diff is the wheels are not locked ,,, meaning that a force of 50 ft LBS will make them slip so that one wheel will rotate at a different speed than the other. this is where that modifier comes in to play.....

  5. #5

    Default

    Well I'm a ROYAL PURPLE kinda guy. Tried and tried in my Harley Davidson.... I just put the MAX GEAR in the front and MAX TRANSMISSION in (equal to the Dexron), next is the rear.... What does it hold, about 4 quarts ??????

  6. #6

    Default

    Quote Originally Posted by Jeff Dodson View Post
    Well I'm a ROYAL PURPLE kinda guy. Tried and tried in my Harley Davidson.... I just put the MAX GEAR in the front and MAX TRANSMISSION in (equal to the Dexron), next is the rear.... What does it hold, about 4 quarts ??????
    Jeff...buy 3-Quarts, as the 10-Bolt Rear Diffs takes about 2-1/2 quarts to fill.


    MIKE


    99"SILVERADO
    5.3 l 3.73 l G80
    BLACK BEAR CUSTOM TUNE
    SNUGTOP l COLORMATCH l KATZKIN










  7. #7
    Legend

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    the amsoil site I listed here has all that info... amounts and the proper fluids.

  8. #8

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    Quote Originally Posted by j cat View Post
    the amsoil site I listed here has all that info... amounts and the proper fluids.
    Yea I read that, was just posting what I had done. 80 bucks on 2 for the front and 2 for the Tcase , damn RP is expensive

  9. #9
    Legend

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    the royal purple is expensive ..

  10. #10

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    Quote Originally Posted by j cat View Post
    the royal purple is expensive ..
    Not much more than any other SYN OIL... Besides that, ITS THE BEST and this truck has 250 k and I want it to last longer

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