Feels Like Getting Bumped.

[KeepinItFord]

Today i stopped at a light, and i when i went to go it felt like the person behind me like tapped my bumper, but they were far back, so i was like hmm? and its been doing it every time i left off the brake after i stop, i left off the brake and before i step on the gas it feels like i get tapped. i checked my U joints, and i have a broken one in the fron, but its not in 4wheel, and the hubs arent locked.. any ideas?

[KeepinItFord]

Bump Bump, ,wtf is wrong with my truck! lol im so depressed because of this.

[GreenF350]

Ok....Well, here are a few things to look into. Not sure of the exact driveline setup on the OBS, so if you don't have something I mention, just move on to the next one.

1. U-Joints
2. Carrier Bearing
3. Transmission Mount (I suppose it wouldn't hurt to check the motor mounts too).
4. Grease the slip yoke in the driveshaft (If no fitting, pull apart and grease)
5. U-Bolts that hold axle to springs
6. Bushings in rear springs/shackles
7. Particularly if manual trans, but either way...Slop in rear differential
8. Oh yeah, don't forget to check for loose hardware where the driveshaft connects to the transmission/transfer case and differential. I have recently seen two Superduty's with loose bolts at the transfer case for no apparent reason (Mine was one of them and I haven't touched the driveshaft in over 2 years!)

I'm sure I have missed a few things and there are a few things I listed that aren't likely to be the problem, but it should get you started. Good luck.
-Aaron

[KeepinItFord]

thanks man, it was my U bolts. theyre loose as f"ck

[GreenF350]

Good deal, glad you got them tightened up. Mine kept loosening up with the 6" block stacked in there and F250ghost actually had his axle u-bolts come loose while he was driving and snap the center pin on the leaf springs. Be glad you found it when you did!
-Aaron