I just bought a '95 F350 2wd PSD w/ a 5 spd, 211, 000 miles w/ a few issues.

Fuel pump leaking, brakes not working, flywheel making noise, needs tires.

My son and I just replaced rear brakes, booster, master cylinder, u-joints, and tires.
My mechanic replaced mechanical fuel pump and fuel filter restriction sensor.

We are getting vibration somewhere in the drive train at 50-55 mph. It is a pretty loud whoom .. whoom .. whoom sound. It stops making noise if I coast in neutral at the same speed.

What could it be? flywheel, drive shaft, rear end, ??? I need your help!

 

shake down the u joints. check for missing weights on the driveshaft. check these then let us know. also, is there any noises that only occur around turns.

 

Look at all the Ujoints real close. Look for red dust. If you see dust, that's your cluprit. My second guess is the carrier bearing. Grab the driveshaft and wiggle it up and down in the middle. There will be some play, but just from the rubber. It shouldn't be much. Think about it like this, it's gotta be something that controls the movement of the shaft cuz it only happens under load. Or the crank balance it shot, because it goes away after you let the RPM's drop.

 

We've given the drive shaft a thorough check. The rubber on the carrier bearing is definitely worn and I will replace it soon--but I don't think it is the source of the problem. No weights missing, u-joints look fine.

I'm going to start a new thread related to what I think is the problem-->dual-mass flywheel vibration. Thanks for your help.