I have a 2008 FX4 that has 108k on the odo. Recently during a rear diff fluid change I discovered fine particles piled on about 1/2-3/4 inch deep on the magnetic drain plug. I figured that the rear diff LS clutches are toasted. The truck shudders around turns, and now constantly driving the truck just vibrates and has a very annoying loss in MPG. I am considering just dumping the stock LS diff for a different differential. I have looked at Detroit tru trac, but want to know if this will be a good differential for lite off road conditions, and if it is good on the street?

Also looking on the 4wheelparts website their are 2 different types for the axle splines. I think 34 spline and 28 spline are the options I saw. Can someone chime in with what is recommended?

 

Did you put friction modifier in when you changed the fluid?

 

Yes after the gear swap and then after break in period, and after a recent gear oil change.

I noticed I had fine particles on the end of my dip stick (after market diff cover) I decided to drain the oil and found enough particles on the drain plug to make me think the clutches are finally shot. Just to get by until I can get True Trac I filled with new oil and added friction modifier.

I did a little more research and found my answer on the rear diff. Now I just want to know some feedback on the True Trac. Road characteristics, off/on road.

 

Wow- Had my mechanic check into my differential problem. We found that the thin shims were walking out on the left side of the diff. They were chewed down enough to be sticking out and rubbing the axle. So pulled the diff out re-shimed and placed the thin shims in the proper place -walla- No more shudder, truck has less vibration and roughness to it. Wish I had a camera to show how nasty the shims looked.

Very glad that the shims hadn't fallen off. I would have hated to see anything else torn up.

My faith is restored in my truck.