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Discussion Starter · #1 ·
I just had a 2.5" lift and 33X12.5X15 wheels installed on my 2002 Wrangler. Then jeep rides fine but at 30mph it has a little vibration and it lasts until I get to 40mph and then stops. My jeep has an automatic transmission. Any ideas what it could be?
 

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Oh and the rear axle is probably not centered either. That will cause a little rear end shimmy on take off. Either need a rear trackbar bracket or invest in a rear adjustable trackbar
 

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Speed sensitive shimmys are almost always tire balance. If it were drive line vibes, it would keep getting worse the faster you went. Go back to your tire shop and have them rebalance your tires...close isn't good enough for larger tires.
 

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Discussion Starter · #6 ·
The vibration only happens when I'm giving it gas, when I let off the gas it stops.
 

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The vibration only happens when I'm giving it gas, when I let off the gas it stops.
Try a couple of washers on the t-case. You may also want to check the condition of your u-joints. Sometimes marginal ones will not produce vibes at stock drive line angles, but will become noticeable with slightly increased angles.
 

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I had a similar issue (stock jeep though) and it turned out to be the U joints. Replaced those and it rides smooth as glass now!
 

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Discussion Starter · #11 ·
Just had the u-joints replaced and it still has the vibration. The mechanic told me to check with the person that installed the lift to see if there were some brackets for something. This is all Greek to me. Does any of that make sense?
 

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Oh and the rear axle is probably not centered either. That will cause a little rear end shimmy on take off. Either need a rear trackbar bracket or invest in a rear adjustable trackbar
Uncentered axles will not cause issues
 

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Just had the u-joints replaced and it still has the vibration. The mechanic told me to check with the person that installed the lift to see if there were some brackets for something. This is all Greek to me. Does any of that make sense?
Did you try some washers between the frame and t-case skid? There are no "brackets" that would cause drive line vibes.

If you had a shop install the lift, take it back to them and let them figure it out.
 

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Discussion Starter · #14 ·
Going to add the washers this weekend. We let you know how that works out. Thanks for all of the input from everyone!!!
 

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Why does the rear axle move off-center when you install a lift?
The TJ has a fixed length trackbar that holds the axle in place (in terms of movement from left to right). It does this by one end mounting to a bracket on the drivers side of the rear axle and the other mounting to the frame on the passenger side of the jeep. When you lift the vehicle that trackbar needs to be longer to recenter the axle.
 

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I lifted 3" and tucked the transfer case skid then had the same vibrations you described. Installed a motor mount lift to correct the driveline angles and it went away.

I agreed about the tire balancing ... you want to shop for a garage that advertises "dynamic wheel balance."
 

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Why does the rear axle move off-center when you install a lift?
The axle is connected to the frame in a Z configuration by the track bar. The top horizontal is the frame. The bottom is the axle. The diagional is the the track bar. Increase the distance (add a lift) and the axle move one way. Decrease and it moves the other
 
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