Odd wobble at highway speed only when accelerating

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kb9mfd

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I bought a '04 KJ for my wife, which was rather cheap and needed some work. When I got it, it was not operational because a rocker fell off. I replaced the rockers and lash adapters so I can now drive it. In town, driving is fine, with no issues. When you get to about 50 mph or more, let off the gas and cruise; when you press the accelerator again to speed up, like to go up a hill or to gain speed, it wobbles back and forth, almost like the rear is slipping in the snow, then stops after about one or two wobbles. I verified it's not in 4WD. It's like all the power only goes to one side for a second or the power distribution is not even between the wheels. This is going straight, not during a turn. Any insight into this strange wobble? Again, it's only when going over 50 mph; I cannot feel any difference under that; when going 30 or driving around town, you don't feel it wobble at all, only when going fast, and the faster you go, the more prominent it is. Just was thinking, is that a sign of a loose track bar or control arms? Thanks!
 

seafish

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The rear lower control arms bushings are worn out allowing front to back axle movement under acceleration.
There was actually a recall on the RCAs for some KJ;s and if it hasn't been done yet, you can get them replaced at a dealership under the recall.
Otherwise, you'll need to buy a pair of the upgraded ones and replace them EZPZ.

That said, you should check the rear upper control arm bushings and balljoint while you're under there….be sure to pressure wash everything over and around the rear axle to keep lotta dirt from falling into your eyes. ;)
 

kb9mfd

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The rear lower control arms bushings are worn out allowing front to back axle movement under acceleration.
There was actually a recall on the RCAs for some KJ;s and if it hasn't been done yet, you can get them replaced at a dealership under the recall.
Otherwise, you'll need to buy a pair of the upgraded ones and replace them EZPZ.

That said, you should check the rear upper control arm bushings and balljoint while you're under there….be sure to pressure wash everything over and around the rear axle to keep lotta dirt from falling into your eyes. ;)
Thanks! That makes sense, I will look into that.

Update - I looked up the VIN and no, it has not been fixed by the dealership and is under the recall. So yay, I can have them fix it :D
 
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Hulq

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My Liberty started to do something similar, turns out it was the drive shaft u-joints. Thought it was the Transmission at first.
 

Trixie

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I bought a '04 KJ for my wife, which was rather cheap and needed some work. When I got it, it was not operational because a rocker fell off. I replaced the rockers and lash adapters so I can now drive it. In town, driving is fine, with no issues. When you get to about 50 mph or more, let off the gas and cruise; when you press the accelerator again to speed up, like to go up a hill or to gain speed, it wobbles back and forth, almost like the rear is slipping in the snow, then stops after about one or two wobbles. I verified it's not in 4WD. It's like all the power only goes to one side for a second or the power distribution is not even between the wheels. This is going straight, not during a turn. Any insight into this strange wobble? Again, it's only when going over 50 mph; I cannot feel any difference under that; when going 30 or driving around town, you don't feel it wobble at all, only when going fast, and the faster you go, the more prominent it is. Just was thinking, is that a sign of a loose track bar or control arms? Thanks!
Similar issue for me!
 

kb9mfd

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Well then call a dealership near you with your VIN to see if the replacement LCAs have been installed yet.
I did, and they said to have it there on Monday. You can look up the VIN online, and it will tell you what recalls it has and if they were done. That recall was not ever done, but the other two were, so I am good with those.
 

kb9mfd

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My Liberty started to do something similar, turns out it was the drive shaft u-joints. Thought it was the Transmission at first.
If replacing the lower control arms does not do it, I will look at that next. Thanks!
 

seafish

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I did, and they said to have it there on Monday. You can look up the VIN online, and it will tell you what recalls it has and if they were done. That recall was not ever done, but the other two were, so I am good with those.

Ya … was talking to Trixie who posted same problem after you. ;)
 

Robochop

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I also experienced this and it ended up being the short 4x4 shaft. I ordered a kit on Ebay and rebuilt it myself!
 
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