EXGM Posted January 4, 2015 Report Share Posted January 4, 2015 (edited) So I decided to service rear diff this weekend now that truck just cracked 50k. I went to dealer and got fluid and friction modifier for rear end. I am getting conflicting info, owners manual doesn't call out specifically. I added friction modifier for the limited slip but other things I found online (so you know its true) say not to use. What is correct? Can someone help? I hope I don't have to drain again.... Truck is 06 RWD Edited January 4, 2015 by EXGM (see edit history) Quote Link to comment Share on other sites More sharing options...
JC03SS Posted January 4, 2015 Report Share Posted January 4, 2015 You do not need to put that in the rear. I wouldn't!! A good synthetic fluid is all you need. Quote Link to comment Share on other sites More sharing options...
Aldofashow Posted January 4, 2015 Report Share Posted January 4, 2015 (edited) Found this for ya #14 fluids for tranny trans case front and rear diffs: post #14 zippy The special Admin 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. Edited January 4, 2015 by Aldofashow (see edit history) Quote Link to comment Share on other sites More sharing options...
EXGM Posted January 5, 2015 Author Report Share Posted January 5, 2015 Great that's what I thought... opps expensive mistake. Looks like I will drain this weekend Quote Link to comment Share on other sites More sharing options...
levilz Posted January 17, 2015 Report Share Posted January 17, 2015 https://www.amsoil.com/shop/by-product/gear-lube/severe-gear-75w-90/?code=SVGQT-EA GM calls for 4.2 pt, so it would be 2.1qt. The front diff uses the same Severe Gear 75W90 and would take another 3.4-3.6pt, so 4qt would do both. If you would like to try some out, let me know. I could probably ship it to your door for around the same price or a little cheaper than you could get it from a retailer there. Quote Link to comment Share on other sites More sharing options...
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