06 F250 vibration at speed
Hey folks, new to the forum, and new to diesel ownership. I just purchased a new-to-me 2006 F250 FX4. I has 164K on it. It's in great shape, looks like the previous owner took good care of it.
I am experiencing a vibration/low freq hum somewhere in the driveline. It has done this from day one, but has seemed to gotten worse recently after I have done some work. It looks like the previous owner had hit something pretty hard on the left rear tire, as the rim had a chunk taken out of it. I replaced my wheels all the way around with some aftermarket rims, and kept the same tires, as they are almost new (stock 17's). While I was doing all of this, I noticed the U bolts holding the axle to the spring, as well as the alignment bolt that goes through the leaf springs, were bent pretty good. I replaced all of these, and it straightnened up the rear end. I then took it and had it aligned, since previously, after they smaked it around, they just realigned it. So now my truck tracks straight, and all looks good. Also, the tires were balanced and inspected by the ford shop, and i was told they were good, not out of round. The only issue is that it seems to have made the vibration worse. I can reproduce it one of 2 ways:
1. Get on the gas hard from a stop, and it will do it until I let off the gas, be it 20 or 70 MPH. As soon as I let completely off the gas, it subsides somewhat, to where it is pretty much gone.
2. Hit the gas pretty good anywhere over 40mph or so, and once again, it seems to go away almost completely after I let off.
I am going to replace all the U joints and carrier bearing Friday.
I also dropped the rear end pan and inspected, it looks good, and refilled with royal purple synthetic gear lube.
I checked the level in the transfer case, and it looks good. I did not change the fluid though.
After the ujoints/carrier bearing, I'm out of ideas. Any help would be appreciated.