Yes I did a search...I have a 97 F150 4X2 reg cab flareside...Around 80 I'm getting a pretty bad vibration from the rear when i let off the gas and torque is fed through the wheels back through the driveshaft... I've looked at my drive shaft ..It seems O.K. U joints are tight..THe slip yolk goes up and down about 1/4 inch when I move it by hand..Is that too much? Thats the only thing I can think of...Theres no tranny oil leaking either??

any help? Should i replace the u's and have it balanced? 71,000 miles

 

That is a classic sign of a driveshaft that is too short. Is the driveshaft un modified? The reason being that when you are on the gas the axle wrap pushes the slip yoke in a little bit and it won't vibrate when you let off the shaft pulls out a little and will vibrate. Usually though you will see some oil around the tail shaft because the seal has been beaten out of it. IMHO 1/4 inch is way too much slop at the tail housing. Are you sure all the play is there and not in the tranny mount? I would take the shaft out and have ujoints checked and have it balanced. It usually costs 30 bucks or so for the balancing if there is nothing wrong with it (money well spent when tracking down a driveline vibration.

Hope that helps

 

Well i'm lowered 3.5 inches...Yes I added shims....I also have Metco traction bars...So no wrap..All the power is getting forced through the u's and wheels..?? I think I'm going to pull the shaft..


P.S. THANK YOU !!!

 

Did you remove the U-Joints to inspect them? When I got my F-150 (used) it had bad vibration around 80- 100. The U-joints looked ok and there was no play or clunking. When I removed 'em I found one joint had seized. The roller bearings were broken and fused making it appear tight. Well, it was REALLY tight! It just didn't work! Replacing all three U-joints with Super Duty ones (with grease nipples) solved the problem completely.