I'm driving a 2004 4x4 and when I take off there's a noticable shudder in the rear diff. It's more like it catches 3 times with a bump then all is good. A friend of mine had a similar problem and was told it was the limited slip clutches in the diff that were slipping. The shop said they cleaned them. Is that BS of is it possible to do this. I have the same diff as his Sport Trac. Also, I just had the pinion seal replaced. Wrong gear oil maybe?

 

There is an oil additive called a "friction modifier" that is meant to stop the clutch shudder. If none has been added, then that might be the problem.

 

as stated you need the friction additive,,,,,also some trucks have a slipyoke in the driveline that needs servicing