blue thunder06

Ill be going down the freeway from 50-65 mph let off the gas then lightly press on the gas and it makes a high pitched hum, let off the gas and the hum stops so on and so forth. I had my mechanic take a look, the u-joint was good just out of curiosity. Put some diff additive in it and if my service records are right it was changed in the passed two years

rustyninja911

iTrader: (1)

It sounds to me like it's time to get your pinion bearing looked at

mrgooden

+1 on the rear end.

Richard

BIGDAWG78

yup sounds like read diff to me... good luck

blue thunder06

Why do you say it could be the pinion bearing?

homerstruck

Mine did the same thing, it was the pinion bearing.

rustyninja911

iTrader: (1)

It's just like any other moving piece, it can get warn down and cause the same noise you are describing, and my truck has the same problem

chargeron

My 06 screw 4x4 does the exact same thing. I thought there was a TSB on it. Some sort of kit Ford had to solve the problem that replaced a a couple of rear diff seals I think.

blue thunder06

If y'all don't mind me asking how much did y'all pay to have it fixed?

mrgooden

On my old 84 F150, I let it hum for 60k plus miles.

Richard