I've had a whining from my differential for a few years now. It's a '95 Ram 1500.

Is there an additive or heavier fluid I could use to help prolong it's life a bit, especially with hot summer driving coming up ?

don't want to install a new differential as I'll probably sell the in awhile.

 

You can try 85w-140, or oreilly's auto has straight 140W, I don't know if this will prolong its life but may quiet it down a little.

 

If you have a Diff whine then one of the bearings are gone or about to let loose all together. but then again I have also had ujoints make noise's also. And they are way easier to change out.