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TCase Question

Discussion in 'Chevy Silverado Forum (GMC Sierra)' started by Z-71, Nov 22, 2013.

  1. Z-71

    Z-71 Rockstar 100 Posts

    My 99 Sierra has push button 4wd but not the "auto" button so would my Tcase be auto or manual? The truck manual makes it sound like it is auto but everything that I have read online has made it seem that it is manual. Please help I need to know if I should put ATF or Autotrac II in it. Thanks
  2. clgoch187

    clgoch187 Rockstar 4 Years 500 Posts

    I might be wrong here but id say use the atf....that what most use toll you get to the newer ones with the blue transfer case fluid. And there isntuch difference between the manual levered and push buttons, it just an electric motor that turns the shaft instead of a lever. If nothin else check your owners manual
  3. j cat

    j cat Rockstar 4 Years 1000 Posts

    manual is when you have a lever ..since you have push buttons this is automatic.

    auto 4X4 is an added feature to the 4X4 selection with the automatic 4wd.

    now gm was using Dexron III in these transfercases. what GM did was replace this with the new improved trac II fluid.

    I would call a dealership and with your vin they will tell you what to use and if they have the fluid in stock. you will need a little over 2 qts. only torque the plugs to 15 ft lbs..too tight you will crack the case. case is soft metal. open the fill plug first.drain with the vehicle warmed up from operation..

    the transfercase works all the time ...so even it you do not use 4X4 very much it requires regular fluid replacing.
  4. Pikey

    Pikey Moderator Staff Member 2 Years ROTM Winner 1000 Posts

    nI would look at your rpo code in the glove box. the tcase code start with an N like NP8.
  5. Z-71

    Z-71 Rockstar 100 Posts

    Yes, Calling the dealership sounds like a good idea. Thanks

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    I have two RPO codes that start with NP.... NP5 and NP8
  6. RayVoy

    RayVoy Well-Known Member 2 Years 1000 Posts

    Try this site: http://www.rpocodes.com/

    NP5 is the steering wheel

    NP8 is the t-case (it's called an active t-case)
  7. Pikey

    Pikey Moderator Staff Member 2 Years ROTM Winner 1000 Posts

    if you have RPO code "NP8" you have the NVG246 transfer case.
    The transfer case requires Auto TracĀ® II Fluid GM P/N 12378508
  8. Z-71

    Z-71 Rockstar 100 Posts

    Thank you.... Someone put Trans fluid in it, Do you think any damage was done?

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    Thanks I will check that site out
    Last edited: Nov 24, 2013
  9. j cat

    j cat Rockstar 4 Years 1000 Posts

    no but trac II is a better fluid. as I stated before GM used this dexron III back when your vehicle was OEM built. could be the OEM 1999 fluid still in it !
  10. Z-71

    Z-71 Rockstar 100 Posts

    Thanks, I guess I will be buying some fluid and do a fluid change then.

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