Smitty of Aledo

I just bought a used 04 F150 and started noticing a whine coming when I accelerate, disappears when I let off the accelerator. Anyone else have the same problem?

I took it to Firestone for fluid change and there mechanic told me it needs a new rear end. He wants $3500 to do a rear end. No chance I can afford that? Any recommendations?

BadFish523

Couple questions. Does it have a Limited Slip rear end? Does it rumble or chatter on slow turns? Has the rear end ever been serviced?


If you answer yes to any of these the read this: https://www.f150forum.com/f4/distinc...r-power-32922/ The 5th post down has the service bulletin for the LS rear end. If you don't have a LS rear end then this doesn't apply.

BadFish523

Also I just noticed the TSB is only for replacing the clutch packs. The option to try first if you have a LS rear is to change the differential fluid and ADD friction modifier BEOFRE you add the new oil. Even if the oil you use says it contains friction modifier you need to add Motorcraft stuff. It works much better!

Taildragger

^ It doesn't sound like the OP is describing a LS issue.

BadFish523

Possibly not but my wifes Explorer has the LS issue and it whines during accel and it becomes more of a light very faint rumble when letting off. I realize the clutches are not really in play very much while driving straight but just advising from experience. After I serviced the rear end as I stated above the whine is almost gone.

PerryB

Rear end noises that can be manipulated by throttle input are almost always pinion bearing issues, or loss of preload - which is still a bearing issue.