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4 Wheel Drive/SUVs/98 Jeep GC: Vibration at certain speed

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Expert: - 4/20/2004


Question
Hi, I own a 98 Jeep Grand Cherokee Laredo (6 cyl.) with 68500 miles on the odometer. In the speed range between approx. 62 to 67 Mph (2000 to 2100 rpm), a significant vibration of the whole car and the interior is noticeable. In addition to that, the noise level raises instantly.
When driving faster than 67 Mph the vibration and the noise become “normal” again. This is also the case when driving slower than 62 Mph. The problem seems to be speed-dependent (and limited to a certain range), as in a lower gear with an rpm of 2000 or 2100, there's nothing extraordinary noticeable.
P.S. I got the tires balanced and rotated, but nothing changed. Any ideas?
Thanks.


Answer
Christopher,

I would still suspect a tire problem.  See if you can find a shop that does wheel balancing with the tire still mounted to the Jeep.  Many tire shops, or alignment shops can do this.  It wouldn't hurt to have the front end aligned, and have all the bearings checked.  Other than that, you may have some bad universal joints, or a driveline that has become unbalanced.  For this, you may need to go to a driveline shop.  If none of these appear to be the problem, check your motor or transmission mounts.  I have seen this problem with some automatics transmissions when they start to go bad..

  Carl  

4 Wheel Drive/SUVs

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Carl Brandt

Expertise

Will discuss suspensions, lifts, lockers along with tire suggestions. Trail ratings and possible requirements needed for specific type of trails. Safety equipment and what you should carry with you. Certified off-road instructor. I am not a mechanic, and 4-Wheeling is a hobby, so if I can't answer a technical question it is due to my mechanical knowledge being related to vehicles that I have owned, or have worked on. I do not have manuals on all vehicles.

Experience

40 plus years of 4 wheeling in a variety of vehicles. At the present time, my major off-road rig is a 94 Jeep Wrangler with a spring over and a 1 1/2" suspension lift. This gives me a total lift of 7" or so. I have lockers front and rear. I have removed the track bars, and sway bar for maximum articulation. I am running a stock 2.5 ltr 4 cylinder with a Jacobs ignition along with a cold air high flow filter. It has 4.56:1 gears with a Dodge NV4500 transmission along with a 3.8:1 Atlas II transfer case. This gives me a final ratio of 105:1 in low gear/low range. Other vehicles I own, are a 96 Ford F-250 with a 6" lift, posi rear end, 36" Hummer tires, 5 speed with a fuel injected 460 ci engine, an 87 Samurai with an 8" lift, Ford 9" rear end with a spool, Chevy Dana 44 front end with an electric locker, 5.88 gears, 16% reduction in high range and a 6.5:1 low range with 35" Baja Claws, and a stock 2003 Grand Cherokee Overland. Trails I have run are the Rubicon (10 times), Dusey Ershim, Fordyce Creek trail, McGrew trail, several trails in Moab, Utah along with local monthly runs.

Organizations
Lost Coast 4x4's Cal 4-Wheel Corva UFWDA Blue Ribbon Coalition

Education/Credentials
Certified off-road instructor - Certificates in engineering/electronics

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