Since November my 97' 5.4 with the 9.75 LS 3.55 rear has been making the typical shutter sound and symptoms of a rear end in need for a clutch pack. Changed the fluid and added friction modifier (yes correct weight and amount) and it didnt seem to solve the problem which I was hoping would be a quick fix since im low on cash. Finally took it to the shop the other day and it just so happened that my check engine light came on on my way there = egr valve insufficient. Since It was at the shop I told them to fix that while there at it. Gave them a call the next day and both mechanics could not feel the vibration/shudder from the rear end like a worn out clutch pack would do. They also said that it wasnt the egr valve but the ptfe sensor or whatever it is that has to do with the egr system. $200 later I got a new sensor and hoses. Went and picked it up and tried my hardest on the way home to get the rear end to shudder but it woulnt do it. Does the egr/ptfe sensor system have to do with the rear end at all? Or could the loss of power from the motor because of the malfunction cause a shudder like this?

 

Its the DPFE sensor and my experiance with them has been they dont affect the way the truck runs much at all..Maybe it just took awhile for the new oil to loosen that clutch pack up.

 

I agree that it just took a while for the friction modifier to get worked in. The DPFE does control the EGR and could cause that code, it can also be caused by a plugged up EGR passage in the intake.