dirtbiker545

i have a 1993 ford f150 4x4 5.0L the problem i'm haveing with it is that when you hit about 40mph i start to hear a huming sound, but if i take my foot off the gas it goes away . i check the rear end fulid but it's good. let me know what you think it could be.
p.s. the truck has done this sense i bought it about 6months ago

ScottyD

Does it clunk when you go from reverse to drive or vice versa? If so check u-joints, I would check them anyway, stock ones don't have grease fittings.

dirtbiker545

yes it does i'll try that

Kattumaram

The pinion bearing preload may be slightly off allowing the pinion shaft to shift back and forth very slightly, but enough to cause gear noise, fairly common among the 8.8" differentials. If it's not too loud or annoying, I'd let it run.

Good old Bill

Most rear end howls that can be controlled by the throttle, either accel or decell (drive or coast) will be just as Kat has stated, the pinion bearings. An excellent place to start.