I really need some help here guys? Fighting vibration battle with my 00 xj. It starts around 55 mph and getting stronger with speed increase. Vibrates way harder on acceleration.
Wheels are balanced
New tires less then 6 mo
New control arms upper and lower
New motor mounts and tranny mount
New u joints on rear driveshaft
Front was checked and driveline shop found no problem
New track bar and tie rods
Hubs are checked and there is no play
New steering stabilizer
Alignment is done less then 3 month ago
Steering box replaced
New shocks all around

Should I try to road force balance the tires?
Could it be ball joints or front axle u-joints and no one can notice the issue?
Anything else I’m missing?
Any suggestions how to diagnose?
I attached a video of me jacking a rear end and spinning a wheel back and forth. Some one on Club XJ forum told me it could something wrong with the rear diff. Any help appreciated.

 

What brand and size of tires? They look very low profile to me.
What is the tire pressure?

What kind of wheels? Are they stock steel wheels or are they custom alloy?

In your other thread you said you had hit a pothole hard. Have you
inspected the wheels for cracks, dents or other damage? Especially
the wheel that hit the pothole. A pothole could also damage the inner
cords of a tire.

 

225/75/15 Firestone destination on stock alloys. 33 - 35 psi. The shop told me that rims are not in the best shape but they got balanced. Is there a way to check those wheels? Road force balance? I have a full size spare with an old tire should I replace wheels one by one and test? Thank you.

 

rotate front tires to back to see if it goes away or stays.

 

Tried it today no changes. ;(

 

I know you said the track bar is new but remove the side where its bolted on passengers side and check the hole. Mine did this around 60mph and I said hell with it and rebuilt the entire frontend but besides the control arms being rusted out found the hole was walleyed allow bolt to move.

 

You look a little lifted. What's the driveshaft/pinion angle?

 

Is it a fast or slow vibration? By that I mean if it is a tire it will vibrate at the speed the wheels rotate, if it is a drive shaft it will vibrate approximately 3.5 times faster depending on the axle gear ratio. This will help zero in on the source.

 

Here is something I have done when chasing vibrations. Try removing the
front driveshaft and then drive it on the highway awhile...

When did the vibration start? Was the Jeep that way when you bought it?
Did any of those repairs seem to make the vibration better or worse?

When the repairs were done, was everything tightened to the specs in the
Factory manual? If it is possible they were not, that would be important to do.

As country2 said, check to see if the track bar hole is wallowed out. Then
torque the bolt back down to 75ft lbs or better. Make sure all 6 of the bracket
bolts are tight. Check the bracket for cracks front and back.

TORQUE CHART

DESCRIPTION TORQUE
Shock Absorber
Upper Nut . . . . . . . . . . . . . . . . . 11 N·m (8 ft. lbs.)
Lower Nut . . . . . . . . . . . . . . . . 23 N·m (17 ft. lbs.)
Suspension Arm Upper
Front Nut . . . . . . . . . . . . . . . . 74 N·m (55 ft. lbs.)
Rear Nut . . . . . . . . . . . . . . . . . 89 N·m (66 ft. lbs.)
Suspension Arm Lower
Front Nut . . . . . . . . . . . . . . . 115 N·m (85 ft. lbs.)
Rear Nut . . . . . . . . . . . . . . . . 115 N·m (85 ft. lbs.)
Stabilizer Bar
Clamp Bolt . . . . . . . . . . . . . . . 54 N·m (40 ft. lbs.)
Link Upper Nut . . . . . . . . . . . 36 N·m (27 ft. lbs.)
Link Lower Nut . . . . . . . . . . . 95 N·m (70 ft. lbs.)
Track Bar
Ball Stud Nut . . . . . . . . . . . . . 81 N·m (60 ft. lbs.)
Axle Bracket Bolt . . . . . . . . . 100 N·m (74 ft. lbs.)
Track Bar Bracket
Bolts . . . . . . . . . . . . . . . . . . . 125 N·m (92 ft. lbs.)
Nut . . . . . . . . . . . . . . . . . . . . 100 N·m (74 ft. lbs.)
Support Bolts . . . . . . . . . . . . . 42 N·m (31 ft. lbs.)
Hub/Bearing
Bolts . . . . . . . . . . . . . . . . . . . 102 N·m (75 ft. lbs.)
Axle Nut . . . . . . . . . . . . . . . 237 N·m (175 ft. lbs.)

 

​​​​​​​Track bar hole is oval but bolt is tight and rust around shows that is not moving at all

 

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Feels like a slow vibration

 

Never met a mechanic torquing bolts to spec. I just bought a torque wrench I will re-torque all the bolts. thank you for suggestion. Are you talking about steering box bracket?

 

No lift at all new shackles leaf springs and shocks that is it

 

I would go ahead and dab a bit of nail polish or a dab of paint to make sure. If the paint gets broken you know its moving.

 

The track bar bracket.

Over the years I have had two brackets that cracked. Another had the tapered
hole (for the track bar's socket) wallowed out and became unusable.

Sometimes the frame has been known to crack underneath the steering box. Look for any
cracks in that area. Grab the steering shaft and try to shake it- you should not be able to
jiggle it. Rotational movement is normal.

Here is something to do if you have not yet done so. Get someone to help you
and have them start the Jeep in park. Lie down in front of the Jeep and watch as
your helper turns the steering wheel lock to lock. Look/listen for clunks or loose nuts.
Look for movement of the track bar bolt at the axle end. Make sure the track bar bracket
is not moving back and forth on the frame. Make sure the control arm bushings hold
tight and the tie rod ends show no play.