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I am slowly restoring a 2000 Jeep Cherokee Sport with 97K miles to use as a winter/light towing vehicle.

I had some sag in my coil springs and leaf springs and the shocks were shot. So I had my garage replace everything. I got the HD Coil/Leaf springs from Quadratec.com, since I heard good things about them.

I've been driving a few weeks and I seem to be feeling some vibrations:

  1. At idle - very slight vibration
  2. Reverse - vibrations seem to be coming from the front.
  3. In drive, between 35-40MPH
  4. vibrations seem to be less in 4x4 mode.

Had the transmission mount replaced as it was shot. Improved #1.

Guy at the main garage also checked my U-Joints and Drive shafts, said they were OK. He also said it may be vibration because my springs added a slight amount of lift (and based on the Internet, the springs I got may provide a 1"-1.5" lift above stock).

Another solution I read is to get a transfer case spacer and drop that an 1". My Transmission guy said that "he doesn't know how to do this" but it seems rather simple from watching youtube videos.

Would dropping the TC and/or replacing the engine mounts help me or should I look elsewhere?

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  • Is the frequency of the vibration relative to the vehicle speed?
    – HandyHowie
    Oct 30, 2015 at 20:52
  • It's only when in reverse (any speed or stopped) and between 35-40MPH.
    – bigdaveyl
    Oct 30, 2015 at 20:53
  • Are these vehicles manual or auto transmission?
    – HandyHowie
    Oct 30, 2015 at 21:09
  • automatic transmission
    – bigdaveyl
    Oct 30, 2015 at 21:10
  • Have you had the wheels/tires checked for balance since you've had the springs put in? It could be that the shop dislodged a wheel weight in the process of taking them on/off the vehicle.
    – Pᴀᴜʟsᴛᴇʀ2 ♦
    Oct 31, 2015 at 0:09

2 Answers 2

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With the moderate amount of lift you've described (1" to 1.5"), you shouldn't need a to drop your transfer case.

Dropping the transfer case is done to straighten the angles on the front and rear drive shafts. In your case, consider the length of the drive shafts and the amount of lift. I don't know the dimensions of the XJ, but consider the length of the drive shaft, the angle is only slightly affected by a 1" lift.

The rear drive shaft is quite a bit shorter, so the change in angle is more pronounced and more susceptible to drive line vibe, but still shouldn't be enough to cause a drive line vibe. So a vibe related to transfer case position would manifest in the rear first.

Your mechanic checked the U-joints on your driveshaft, but did he check the state of the centering ball on the double-cardan? Did he check if there was any slop in the slip joint in the front drive shaft (rear slip is with the yoke in the transfer case, so not likely coming from there).

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I'm no Jeep expert, but I can tell you with certainty if you are experiencing vibration in park that nothing in your driveline or suspension the cause for said vibration (while stationary) with the exception of the engine and rotating transmission parts. I suspect an engine skip of sort like ignition or fuel delivery.

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