Synthetic Diff Fluid Question...

[lawdog1]

I want to confirm that the diff fluid does not require a friction modifier or limited slip additive. In other words you are safe and correct to use full synthetic 75w-90 with no friction modifier, without adding any limited slip additive. Thanks for the advice, I did read other posts, but just wanted to confirm.

 

[Jengle]

According to the service manual, DO NOT add friction modifier to the AAM rear axle on our trucks.

 

[Bertram65]

You are correct, no additive, says it right in the manual.

 

[Rosco]

I will back up what Jengle and Bertram65 said.

 

[ACerf]

That is what the books says! However, dealer told me that some customers complained of rear end whine! They added the modifier and the sound stopped! It is important to do the 8 figure 8's to work in the new oil. That will tell if there is any whine or not!

 

[Bertram65]

I thought the friction modifier made it so the clutches on a clutch type limited slip could grab because the oil alone did not allow them to get enough friction. I do not see how that could help the AA anti spin as it is all gears with no clutches. I doubt it would hurt anything if it was in there though.

 

[roperteacher]

I would be interested in if the friction additive really did work in the AA axle. Might fix my last tiny bit of rear whine...