Originally Posted By: Jeff7777
First generation Titan 2004.
Differentials on these trucks were too light-duty for the application; mid-size running gear on a full-size engine/frame platform.
After blowing up left-and-right, TSB was issued early on to run 75w-140 in the rear end. Front axle isn't under the same continued stress with how most people use them, but they don't have a spectacular success rate went put to work.
Frankly, I'd just go get some Synpower 75w-140, and dump it in both diffs.