Gearcase and Transfer Case Fluid Change

[AXE]

When I spoke with the TORCO rep at SEMA, a few years ago, he said most differential builders specify regular, ( not synthetic), gear oil because it runs cooler. I have always run regular. I did use synthetic in the final drive on my MC, because it only held 8 ounces. Do what you want but that's the information I received.

TORCO is widely known as a recommended gear oil manufacturer. I never see it around where I live so I use what's available .

I used 75W140 synthetic in my old 2500HD rear diff. Not sure it mattered, but lot's of guys towing heavy seemed to think it helped.

 

[GatorZR2]

Gear oil selection depends on application. If your running pre 2000 differentials, rock crawling or at the local dirt track for a night conventional might be a better option. Conventional gear oil does have better heat properties but poor cold weather properties, it also breaks down quicker and it's thicker. Modern diff's mostly require synthetic gear oil. Synthetic gear oil has the best of both worlds and it last longer and it's better for towing and daily driving. All gear oil foams at a certain temp and shearing is reduced. Even Nascar uses synthetic gear oil. You can't go wrong with Valvoline, Lucas or Amsoil synthetic gear oils.

 

[scubatech]

I used 75W140 synthetic in my old 2500HD rear diff. Not sure it mattered, but lot's of guys towing heavy seemed to think it helped.

We used to get all our oil in bulk of course in a fleet application. I spent 27 years running equipment and servicing all sorts of trucks, loaders, grader, etc. We used a product called Magna - Glide , I believe it was made by Conoco. It was 75W-140. Good heavy duty EP oil.