Stop in for a cup of coffee

Mattax said

If you want thicker for overkill could pack it with grease like the @dukeboy_318 mentioned for the old powerwagons.

No?

That's my point.
Thicker is not better.
Better is the viscosity range that it splashes and sticks to the gears and maintains film strength and shear resistance while getting squeezed between the gears.

I do not know the heat generated in diffs while drag racing, but generally figure the factory selected grades after considerable testing.
Lets see if Direct Connection recommneded different.

Click to expand...

Yep agreed.

Gale Banks has a great video showing this. They made stock diff covers and molds of popular aftermarket ones out of clear acrylic and stuck heat sensors in and put them on a dyno with a camera and a thermal camera showing how the various covers did with the various oils and such.

The conclusion was rather shocking. For example, the cover that kept the diff the coolest and had the best flow. The factory. And this was a consistent across various axle types. The Dana 60, the gym 14 bolt, the Dana 80 etc. Even over his own diff cover.

The conclusion was that unless one was running a pump, all the aftermarket covers that had capacity, the cooler oils stayed at the back of the cover and the rest basically whiplashed and aerated instead of cooling.

I’ll see if I can find the video but it definitely was cool