Handling issues

[Kuato]

Grand Cherokee in the signature.

All new rear suspension components, new track bar, and new shocks and stabilizer bar within the last 30k miles. I did get rear ended about 20k ago, although the body shop reported no frame or suspension damage. But the handling did seem to get worse after that. Alignment is correct, tire wear is even and steering doesn't wander other than what's listed below.

Statically the handling is fine. When you get into a dynamic situation there is a drastic difference in the behavior. From cruise when letting off the gas, there is a definite movement to the right. Get back on the gas, and there's a definite swerve to the left, enough to change lanes if you let it, sometimes quickly.

It's obvious to me that something is shifting in the suspension; to me it feels like the rear is moving, as sometimes when heavy on the gas there will be a squirm in the rear.

Wanted to pick the brains of those that might have an idea of what the problem could be with suggestions for possible solutions.

Thanks in advance.

 

[4D-56]

Do these have a factory anti-sway bar in the back end?

 

[JimPghPA]

While it probably is something in the suspension you should also be sure one or more of your brakes are not dragging (not fully disengaging when you are not using them). Are any of the brakes getting hot when they should not be?

 

[ChrisW]

When you say all new components, does that include any applicable rubber suspension bushings? What you describe sounds like some sort of transmission/diff/engine mount that is torquing when you gas on or gas off...easier for me to visualize in a FWD vehicle but difficult to see where this would be coming from on your RWD vehicle.

 

[yonyon]

Send it back to the repair shop.

Tell them what's wrong. Drive it with someone from the shop in the truck with you, then have him drive it to feel the problem while you're there. Verify that it drives properly before you take it home again.

 

[Rand]

Originally Posted By: yonyon
Send it back to the repair shop.

Tell them what's wrong. Drive it with someone from the shop in the truck with you, then have him drive it to feel the problem while you're there. Verify that it drives properly before you take it home again.


he was rearended 20000 miles ago.

 

[Kuato]

Yup.

 

[yonyon]

Originally Posted By: Rand


he was rearended 20000 miles ago.


Good catch. Sorry about that.

 

[c502cid]

While driving can you see the plane of the left rear tire in your mirror? When you get on/let off the gas, is the tire moving in/out or fore/aft. I'd jack it up on the pumpkin, and push on the tires in many different directions seeing if you can any movement to start. Sounds like a track bar or track bar mount issue to cause that kind of movement. Of course, this is just an internet guess. Without the torque of the engine and road dynamics it's going to be hard to find. Have a buddy follow you and tell you what he sees.

 

[Audios]

The motor mount/trans mount theory is possible. Look there as well.

 

[Kuato]

Thanks everyone.

Yes to swaybar.

Brakes not dragging or heating up.

Suspension parts were replaced, but NOT in conjunction with the accident (body work only)

Parts include all bushings in rear.

Shop has had the vehicle up on the rack, and pried against all parts, said no movement.

Taking it back to repair shop is not possible; we moved from VA to MT last year.

Motor mounts/trans mounts are in good shape with no movement, according to local shop.


I will take it for a drive to see if there is any noticeable deflection in the rear wheels under accel/decel.

 

[gathermewool]

What does rotating the tires from front to rear do?

 

[Kuato]

Originally Posted By: gathermewool
What does rotating the tires from front to rear do?


Same deal both before and after rotation.

 

[OneEyeJack]

Is the rear axle centered behind the front wheels? When you do a panic stop on a slippery surface do you experience any surprises?

 

[Kuato]

Originally Posted By: OneEyeJack
Is the rear axle centered behind the front wheels? When you do a panic stop on a slippery surface do you experience any surprises?


Before the track bar was installed, it was a wild ride in a quick/panic stop.

Since the track bar has been put on, once the initial swerve is done, it stops straight and true.

Frustrating issue, can't find it.

 

[Grebbler]

That sure sounds like a trailing arm allowing one side to slide front to back. When you stomp the gas either the left wheel is moving forward or the right is dropping back - cocking the axle. It would have to move a fair amount to shift you around so badly.

Another goofy thing to check is the axle. If one tube is bent then the truck would be influenced by weight shifting and which tire had the most traction at the moment. I would think that would show up in tire wear.

You could have a bearing binding up under load or, as was mentioned earlier, a sticking brake. Take a drive, use the brakes a lot then feel each wheel near the hub.. If one is hotter than the others you have a friction problem.

Is the differential in good order? Maybe you have 1 wheel drive!

 

[crazyoildude]

jeeps are known for suspension problems check the steering box by moving wheels back and forth with the engine off and see if there is a lot of play in the wheel if there is check the front end with someone shaking the wheel from side to side and see if there is less movement from the box and if so adjust it.. go onlt a 1/4 turn at a time and if you are unsure let someone who has done it before.

 

[OneEyeJack]

Again, the question. Are you sure that the rear wheels are centered behind he front wheels.

 

[Kuato]

Originally Posted By: OneEyeJack
Again, the question. Are you sure that the rear wheels are centered behind he front wheels.


Yes, they are centered; the alignment has been checked.

Apologies for the slow response, but found the issue, thanks to all for suggestions.

Wasn't until today that I could get it up on a rack. "Helped" the technician look around underneath. In this year GC, the upper control arm is a "V" shaped unit that points towards the rear. The left side bushing is cracked and torn(they missed it before and would have missed it today had I not been there)

Will be replacing both bushings and cross your fingers.