Shimmy, Shakin, Rocking Problem..

[SnowyXJ]

Ok.. It's that time of year.. All sorts of problems with my 89 XJ 4dr.. While driving at highway speeds 75-85mph if I hit any sort of bump all of a sudden the jeep rocks back and forth causing me to have to slam on the brakes and take it down to 20mph and then reaccelerate..

I've been told by a few people that are everyday mechanics, that it's probably the track bar..

I've got a 3.5" lift and it's got the stock trackbar with 150,000 miles on it.. so. I don't doubt it that it's the track bar, but I'm looking for suggestions..

I'm just trying to get a parts list together before I get too carried away..

Thanks..

Bill

 

[Harvo]

Have you tried tightening it? They somtimes get loose where they attach to the axle. Mine has worked loose twice. You can't feel that it's loose, but when you put a wrench on there, you'll be able to tell if that's it. Tighten all the bolts / nuts on the trackbar and bracket.

Make sure your rod eds aren't worn out too.

 

[MaXJohnson]

some helpfull information would include tire size, tread type and air pressure, wheel backspacing or offset, castor angle, brand of equipment used for the lift and recent work done or changes made to your Jeep. Did you have it aligned after the lift was installed? What were the alignment specs?

Having the front end shake at that rate of speed is unusual. It is far more common around 45 - 55 MPH. Are you running stiff springs, high air pressure and/or small, narrow tires?

You can cause considerable wear on stock track bar and drag link rod-ends with only a moderate amount of off-roading once you add a 3" lift. Do you take it off road? Do you disconnect your front sway bar?

 

[SnowyXJ]

Michelin 235/75/15 tires All Terrains
3" Combination of custom coils (heavier than normal about 200# more spring rate to accomodate for the never installed plow.)
Rancho Shocks..

And yes it has been off road, but not more than a half dozen times, and never seriously wheeled..

I was running 55psi in the rears and 45psi in the fronts.. but that was due to carryng the weight of the 16' landscape trailer.

Either way..

The recent work that was done was very minimal.. oil change, etc.. etc..

 

[Ludakris]

so it shakes all over the road, then you take it back up to speed? ok.

those sound like some way high pressures for those tires... I would think your running on the center of the tires... only.. I also assume you have your sway bar connected.. that can cause crazy stuff if its not... I dont run mine, but I dont run 75+ either.. have you checked the alignment after the lift.. mine was toed in and did some crazy stuff...

 

[MaXJohnson]

Michelin 235/75/15 tires All Terrains
3" Combination of custom coils (heavier than normal about 200# more spring rate to accomodate for the never installed plow.)
Rancho Shocks..

And yes it has been off road, but not more than a half dozen times, and never seriously wheeled..

I was running 55psi in the rears and 45psi in the fronts.. but that was due to carryng the weight of the 16' landscape trailer.

So... no alignment data? no alignment?

I'd start by dropping the air down to ~ 30 psi and get rid of the stiff coils. Find out what your castor and toe are set at and look for loose front suspension and steering parts. As mentioned, it doesn't take much wheelin' to kill stock drag link and track bar ends with a lift, so those should be suspect. If the Rancho's are adjustable, run them on a softer setting.