Originally Posted By: NHHEMI
Originally Posted By: FrankN4
Originally Posted By: Jim Allen
Originally Posted By: FrankN4
I have a 2008 Silverado that I am getting ready to change the rear axle gear oil. I just today called Mobil 1 about their 75W-90 synthetic and they said it did not meet GM specks. I called Valvoline and they said their 75W-90 synthetic did not meet GM specks, I have not called Amsoil yet but will later today.
If two oil companies say their product does not meet a spec and both recommend using the GM gear oil, I think I am going to do that.
What spec? Is there something new or improved about the '08 that requires some special oil? Just an AAM axle, very much like what's been built for decades and the "official" GM stuff doesn't have a great rep.
I honestly don't understand why someone at either of those companies would tell you what they did but wonder if they offered some specifics?
The owners manual says to use "SAE 15W-90 Synthetic Axle Lubricant (GM part Number US 89021677 Meeting GM Specification 9986115)
I called Mobil and asked them if they met that specification with their synthetic 75W-90. They put me on hold for a very short time, came back and said their synthetic gear lube did not meet GM specification and they did not recommend its use. When I called Valvoline, before I could even finish the spec number they said that was a GM specification and none or their gear lubes would meet that specification, I would have to get that one from the dealer. Neither would talk about specifics, I did ask. Honestly, I don't blame them for saying nothing.
FrankN4;
You meant 75W-90 right not 15W-90!
The part# you provide and the spec # are for 75W-90.
That is just the GM synthetic 75W-90
"Grape Juice". Nothing special about it whatsoever other than it is synthetic and has limited slip additive/friction modifier in it. Well, unless you think that special grape scent makes it better.
People have been running aftermarket synthetic 75W-90's in place of it without any problems whatsoever. Actually the GM "spec" is not even a techincal spec from what I found out but rather it is a packaging spec according to GM. There is a thread here on this site about it( ie the spec # and what it means ).
Any aftermarket synthetic GL-5 gear oil with the LS additive already in it will be fine. The rear end in your 08( should be a G80 going by the recommended fluid )is the same rear end that was in my 05 and 07(NBS )Silverados and has been used for a long time. Nothing special about the GM fluid called for other than synthetic and that it already has the LS additive in it is the bottom line.
It is not like the special blue GM transfer case fluid( Autotrak II )or the special GM AWD fluid( Versatrak )that have no or limited aftermarket replacement fluids. The
"Grape Juice" is easily replaced with aftermarket 75W-90's.
I ran RP MaxGear 75W-90 in both my Silverado's. that called for the exact same fluid as your 08, and it worked fine. No problems, no chatter, no failures, etc... If you prefer Amsoil use their 75W-90( probably the severe gear variety - you can look it up on their site ).
If you are worried about it then just run the GM fluid but you will be paying $25-$30 a bottle vs $15 and less for other alternatives. I would personally throw some RP MaxGear, Amsoil, etc... in there and move on but it is your truck and I respect your decision.
I have an AWD 03 Yukon. I put the Autotrak II in my transfer case. Should I have put this Versatrak fluid in instead or am I ok? I had never heard of the Versatrak.