I have a 2000 F-250 CC,SB,4x4 PSD. About 10,000 miles ago I needed to add some friction modifier to my rear end(service shop didn't add any after fluid change) to stop the shudder. Recently I have noticed the shudder is back. I am wondering if friction modifier wears out or if I have another problem. I notice the shudder only when turning and accelerating at the same time. If I accelerate in a straight line-there is no shudder. Any ideas? thanks

 

i dont think it wears out, you might not have put in enough, it sounds like it needs some more. if you want your LS to work better,put in just enough to stop the shudder around corners, but the clutches will wear out faster. its your choice

 

depending on how many miles you have on your vehicle ,and if you tow alot ,you may have worn clutch packs and a weak spring within the diff.
Try more friction modifier if that helps ,your good,if not consider rebuild or a aftermarket locker.

Rich

 

Thanks for the replies