02 FX4 Supercab 5.4. 6" Fabtech on 35" BFG A/T's on 16.5x12 wheels with 51mm off set. Truck has the "death wobble" between 40-50 mph. Friend says it could possibly be the idler arm. Not too sure. Just had the tires and wheels mounted and balanced today. I didnt have this problem running my 17x8 Pro Comp alloys and 35" Mickey Thompsons. Any advice would be greatly appreciated.

 

Felt where, steering wheel or seat or both? Tire balance is a cheap first try especially if they haven't been done in a while. Next I'd check the tie rods, idler and ball joints as well as the driveshaft? Who knows man, anythings possible.

 

It can be felt from both. I had the tires and wheels balanced today. I drove about 5 or so miles before I felt it. Im thinking the wider wheels were the last straw for the idler arms or tie rod ends. I figured a second opinion wouldn't hurt before I wentand got all new parts and do the work.

 

grab both sides of tire...shake side 2 side...does it stay in place or wobble with u

 

I'd definitely check the tie rods, do you know how to properly? If not, grab one at a time, push and pull up and down, then front to back. It should turn but no clicking within the ball of the rod should be felt. If they are originals, it's likely they're shot. If so, I'd get all replaced if $$$ permit so you'd need only 1 alignment job (I say this because they'll all eventually go). Get grease-able one's with a lifetime warranty. Keep updating.

 

Im willing to bet its the idler arm.

Get someone to move steering wheel while your under the truck, and if you see movement in the idler arm up and down its done...

 

update: I replaced the idler arm and its almost solved the problem. It has a slight wobble at ~55 now. Not nearly as bad as before though. Ill be getting my tires rebalanced before i drop some more money for tie rod ends.

 

With the situation, you should look at the steering box mounting now for being loose due to the problem.
Extending the wheel track center outward makes all this more sensitive.
Anything worn or loose will show up.
Good luck.

 

where did you get the 16.5 wheels!?!?!?

 

That poster hasn't logged in for 6 years now. I doubt you will get a reply.

 

This thread is a decade old. There were tons of 16.5s back then.
Anyways, you can get old welds off the weld facebook group.
Afaik no one makes tires anymore though so 🤷‍♂️