There may already be a thread on this, but i have an 03 f150 fx4 and recently when i ease into the throttle from a dead stop or under around 10mph, i hear this knocking/tapping sound which i think is coming from the drive line. Its anywhere from 3-7 quick knocks. At higher speeds, it doesn't make any noise. Could this be my U joints? I've heard they may do this if they need grease.

 

Possibly limited slip diff issues

 

Clutch packs going bad?

 

Maybe, but change the fluid and use the right friction modifier and see what that does. Cheap stuff first.

 

And if you've never changed the U joints, that wouldn't hurt, but usually U joints will make a whine or howl at higher speeds. Or in my case, a hell of a vibration. The nice part is a U joint is only like $10 each.

 

Alright. I'll see what i can do this weekend. Thanks man.