Help?! I have a F150, 4x4, 5.4 with 120K miles that has developed a slight shudder when starting from a stop (and turning R or L). Its not overly pronounced and there is no grinding noise. I suspect the clutch in the differential. I have also heard that a possible (and far cheaper) fix is to drain and replace the oil in the rear differential first.

Anything I should know before I try to replace the oil? Or should I just go straight to replacing the clutch plate? Would appreciate anyone's input.

Thanks.

Replace the oil in the differential and add 2 bottles of friction modifier. Then drive truck in circles both ways. Make about 20 tight circles both ways.