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fluids for tranny trans case front and rear diffs


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I run royal purple in everything. I could tell a slight difference when I done the transfer case and rear ends. Royal purple is prob the best off the shelf fluids you can buy at the auto parts stores IMO.

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Personally, M1 or Amsoil. Then if I ever changed it would be to Amsoil. Just went through this whole service replacing every single fluid and filter.

Tranny and T-case liquid was swapped out for the same stuff I ran when I had fluids changed in 07.

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  • 2 weeks later...

I recommend 75w90 in front and rear and both to be synthetic for sure. 75w140 is fine if you run in very high temps otherwise stick to 75w90. Royal Purple, Mobil 1, and Amsoil are all very good choices. Make sure to not use any additive in the rear diff as that can cause the clutches to stick together and not allow the diff to unlock. There is an actual bulletin from GM about that specific issue. For the transfercase simply use a Dexron 3 approved fluid either in synthetic or GM form. That is the recommended fluid from GM and the same I'd recommend myself. In GM form Dexron 3 is only sold as manual transmission and transfercase fluid though since Dexron 6 is now the fluid they sell as actual transmission fluid and yet isn't recommended in manual transmissions and transfercases. Don't bother with the Autotrac fluid from GM (blue stuff) either. You will be wasting money on that as it is designed for cases where the fluid contacts the clutch pack. The Silverado SS uses a viscous coupler which is a sealed unit and the transfercase fluid never gets into the viscous coupler unit. If it did that would mean the seal is broken and the unit is failing anyway. The transfercase fluid in the SSS is only there as a lubricant for the bearings and chain as well as there to keep it all cool.

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