On my Savana 3500 with a locking differential, GM recommend using gear oil # 1052271 without friction modifier.


This is the same oil they recommend for the open diff. version, and they say to use a 80W90 or equivalent for this diff.. No word as what is the #1052271.


I am using a synthetic 75W90 oil without a friction modifier, but sometimes, the axle is showing a behavior like it needs the additive. I would like to know if I have to use the friction modifier or not. Is it included in the GM oil already, making it unnecesary to put additionnal additives? Is the GM oil a 80W90 mineral?


I know too that GM has a service bulletin on Rear axle lubricant - recommendations(#01-00-90-001A), but I don't have access to it.http://www.dieselplace.com/forum/smileys/Cry.gif


Thanks for helping.


Richard.Edited by: Richard7

1052271 is just 80/90 lube.


I posted the tsb you referred to in the TSB section for your reference.


If its grabbing on tight turns in the rear, I would install some additive, GM has said that its not necessary but.....I have fixed some just by adding it. If you are already running the 75/90 synthetic, you might try draining and refilling with fresh as it could be loosing its lubricity. There also may be a difference in the clutch material on the posi units that may be just enough to make a lubricant not work as well.


Eric

Thank you for a quick answer!


I find it interesting that the 3500 pick-ups are getting the 75W140 synth. oil, while the 3500 vans use 80W90.


My van weight 6623 lbs empty, is rated by GM to tow a max of 7800 lbs, but I have yet to find how to install a fifth wheel.http://www.dieselplace.com/forum/smileys/Big Smile.gif


Richard.