Ever since I bought my jeep two years ago it's had some weird massive bounce in the front end. Thought the tires we're out of balance. Balanced. Swapped axles to 3.55 from 3.07 and the bounce remained. New shocks. Front axle diff bearings went bad. Swapped axle again and did polyurethane bushings at the same time. Curbed it making a upturn in the snow a little. Death wobble started. Replaced gearbox and all steering parts. Yet the bounce remained. Swapped wheels and tires. The bounce went away briefly. Then came back. Wheel bearings and swapped to cv shafts since I don't go offroading. Brakes started dragging. Replaced calipers, hoses, pads, and rotors. Its been aligned twice and once in the last 60 days. So now almost everything up front has been changed and it still bounces. The speed at which the bounce happens is at 64 and above. At 75-80, it's easy to keep on the road and straight but things fall off the console, dash, and anything else that isn't bolted down. It will smooth out occasionally to like glass then go back to bouncing. Another odd thing is that no matter what, if I turn the wheel all the way to the left, the tires rub the lower control arms. Turn all the way right and they don't rub. The only thing I can think of is maybe the control arms are all out of whack. There is no lift on the front end so the geometry should all be correct. I just want a smooth ride after all this work. I'm bloody flabbergasted.

 

What size and type of tires are you using? What kind of wheels?

 

245/70/16's i can't remember what the brand is but they are more of a road tire. The wheels are Jeep Icons.

 

That's a big tire for an XJ with no lift. No wonder they rub at the stop.

 

But only in one direction? Even the 235/75/15 General grabber at2's rubbed only to the left.

 

I've got 235s on factory XJ wheels and they never rub on either of my XJs.

Have you ever removed the front drive shaft, then driven it?

 

Front drive shaft hasn't been in for a few months because I was too worn out after swapping the front axle again to put it back in and too busy with two jobs to put it back in.

 

So no matter which way you move the tires & wheels around, front to back, side to side, crisscross, the vibration does not change at all?

 

I haven't rotated the tires recently but it's one last thing to try. When I had the generals, it would go away for about 500 miles and then come right back to the oscillation of bounce for a long while, smooth for a short bit, then back to bouncing.

 

Normally when that happens, each tire is a little out of balance or not quite round; and/or one or more wheels have a slight warp to them.

They might balance in the air on a computer balancer and still shake when installed and running on the road all together.

 

Would a bubble balancer be a more accurate balance?

 

I've had a booger of a time with balancing. One kid spun it up with dust and dirt still in the rim! They can, and do get it wrong. Agreed with Firestorm, try some swapping.

" bounce for a long while, smooth for a short bit, then back to bouncing" That could be the tires canceling vibration, then getting bad when the two sides "sink up". Even on a dead straightaway, one tire is some amount different than the other.

My 235's rarely rub on the front. 25 year old springs and no lift.

I doubt the bubble balancer would work better than a modern spin balancer, not sure there though. The is such a thing as "balance beads" Plastic beads that fit through the valve stem, then "magically" distribute themselves for a perfect balance. No experience here and mixed reports.

 

Back to tire size 235/70 does not rub at stock height unless one or both tires are low on air. The only time I have ever had a problem with bouncing was when both front shocks needed replaced on my 98. I don't think this is your case though as you say it only happens above 64mph.

 

Bubble balancers are not accurate enough for today's vehicles.

Don't use balance beads. Or snake oil. Or Fix-A-Flat.

You didn't, did you? Ever? In these tires?

 

I'd suspect you have slight tire imbalance combined with something worn that you haven't changed, such as track bar. The track bar is what keeps the axle from moving side to side. You might also want to make sure your springs and springs mounts are all intact. What I've read here, sometimes when you raise the vehicle off the front tires and set it back down, the problem may go away for a bit.