i have an 06 f150 harley. today i noticed that when i let off the gas i would get a thumping feeling. i have check my tires and they are fine. it is a rhythmic thumping, not a fast thumping but more like thump....thump....thump....ect. there is no change to it at any speed. it reminds me of a flat tire but that is not the case. it does stop when i am at about 20- 15 mph or slower. on accel it is fine. it olny happens when i let off the gas. i have check the u- joints, motor mounts, and tranny mounts. all are solid. any ideas? thanks for the help.

 

It might be the limited slip in your differential on it's way south. Does it make any noises when you turn left or right into a turn?

Another thing you can consider is jacking it up, taking the rear wheels off, and have an assistant accelerate and then let off, while you are under the truck. Sometimes it's the obvious once you can isolate the noise. The inside of the cab can make it sound like it's coming from someplace else.

Just if you do it, please use common sense... treat that driveshaft as a live pto... no loose clothing... don't touch something moving.

 

there are no noises when i turn. i would have to jack the entire truck up to do what you said. it is all wheel drive and 4hi. ive worked on trucks, cars, and bikes before but this one has me puzzled.

 

What do you mean by it is all wheel drive and 4hi? Does this mean you are driving it everywhere in 4hi or are you simply stating that it is a 4x4? I'm not bustin yer chops but I have to ask.

 

my truck is either awd or 4hi. yes it is a 4x4. the 4x4 swith is only awd or 4hi. its an odd ball harley truck.

 

fix the issue i think. though it could be the u-joints. changed them out. problem went away. the old ones didnt look to bad. one of them was starting to go out. then a week later, it would start shuddering when i applied the brake. figured it was time for a brake job any ways. it has almost 80k on it. well i found the problems. the rotors were shot and the rear pads and e-brake shoes were shot. front brake pads still had plenty of meat on them. chaged them out anyway. now all it right in the world now. lets see what happens next week. sorry for taking so long to get back to every one. i work about 6 hours away from where i live and currently working a 7 days on 7 days off schedual and have been working overtime so it more like a 10 and 4 schedual. thanks for the help. ill be on the look out for the other issues you thought it could be. its bound to happen sooner or later.