65,000 miles
Truck just spend 3 days in the shop. I had a bad driveline/front end vibration that felt like something was smacking the floorboards when accelerating and accelerating when turning. This was very very prevolent when towing 12K lbs; also through the mountains.

They replaced 3 U-joints and checked everything else. They replaced my front rotors (separate issue) which involved removing, inspecting, and repacking the front wheel bearings. They inspected the driveshaft hanger bearing and its in good shape too.

I just picked it up from the 4x4 shop and its still vibrating in an accelerating left turn without towing.

What else can I have them look into when it goes back next week?

(no peanut gallery comments; I need this fixed)

Did they spin the driveshaft for ballance? loose motor mount? tires ballanced, any crazy cupping or wear on the tires? just shooting in the air here.

They did not spin the driveshaft to my knowledge. Wouldn't an out of balance driveshaft vibrate a LOT and all the time? Loose motor mount could be a culprit, I will check on that. Its not in the tires. They tires are fairly new, and if it was in the tire I would feel the steering wheel vibrating. The steering wheel is rock solid. Its in the drivetrain as it feels like someone is hitting the floorboards with a rubber mallet when it occurs.

I would have them check engine and trans mounts. I am more of a GM man myself but have seen a simular problem and it was the trans mount.

Found a place where the MBRP exhaust was hitting the cross-member that you could not see unless you were way up wrenched under the truck. I know this is a known issue with the MBRP kit, but everything was tidy when it was installed and it developed over time as the exhaust settled into its best resting position. I think we have all the thumps worked out now. I had it up on two different lifts today with me and two other guys inspecting it. We did not see it until it was up in the air the second time.

Main culprit seamed to be 1 really bad U-joint and 2 that were starting to wear and rust. Once the U-joints were replaced, I could hear the exhaust hitting; of which I was probably hearing/feeling several different issues at once. We were able to isolate and fix each issue and all appears to be good now. I left the truck at the first 4WD Specialty shop again today for a full fluid swap: differentials, transfer case, transmission & filter. I'll pick it up tomorrow and tow with it this weekend.

Motor mounts. Not uncommon on the Fords. They use a pretty soft one that cuts down on vibrations. The downside is they don't last. I don't know about your '00 but on my '03 and my '05 you couldn't tell without replacing them.

I have had customers with same complaint and found front sway bar to axle bushings loose and replaced them with larger update kits to cure the problem. Brian

Thanks everyone. I think its all quiet now, but I will keep an eye on these areas/parts if future thumps develop.

if anything comes back get them to check your carrier bearing, it is the first thing to go usually and if you lifted your truck you change pinion angles and that too causes vibrations unless you shim the bearing down.

andy