Does your Jeep shake quiver, tremble agitate, brandish, bump, chatter, churn, commove, concuss, convulse, discompose, disquiet, disturb, dither, dodder, flap, flicker, flit, flitter, flourish, fluctuate, flutter, jar, jerk, jog, joggle, jolt, jounce, move, oscillate, palpitate, perturb, quail, quake, quaver, rattle, reel, rock, roil, ruffle, set in motion, shimmer, shimmy, shiver, shudder, stagger, stir up, sway, swing, totter, tremor, twitter, upset, vibrate, waggle, water, wave, whip or wobble?
Nothing ruins a great drive in a Jeep faster than the many shakes, wobbles and annoying vibrations that can occur. These problems are made even worse when you start lifting the suspension and adding bigger tires.
The most common cause of shakes and vibrations in a Jeep are the tires. Jeeps use rather large tires often with heavy tread and with stiff sidewalls. All these factors add up to a rough ride if the tires are not well cared for.
Another common source of vibrations are the drive shafts. These rotating shafts have to be perfectly straight, and in proper alignment and balance to run smooth. Often the drive shafts can be misaligned as the Jeep is lifted or if the springs are damaged. They can be easily bent or knocked out of balance through off road use.
The most startling of all Jeep shakes is what we call Death Wobble. Death Wobble is the very scary sensation that occurs when the front wheels start to flutter like bad shopping cart wheel. The only way to deal with it while driving is to slow down until it quits. Right after your life flashes before your eyes.
Lets us look at the tires first. Other than being round and black, truck tires are very different from passenger car tires. Truck tires have much stronger sidewalls and thicker heavier tread. Both of these factors mean they may need much more weight to balance them. Also, as the tread wears the balance may shift.
Also, it is very easy to knock off a wheel weight when driving off road or sometimes move it to another place on the rim. Mud can also build up inside the rim and rocks can lodge in the tread. Any foreign object like this will cause an imbalance.
When you have a speed sensitive vibration, look first to the balance of the tires. It may be necessary to use an internal balancing system to deal with the changes in balance cause by tire wear.
Drive shaft vibrations are sometimes hard to diagnose. When you suspect a drive shaft vibration, start by inspecting the U joints. Make sure all the U joints are properly lubricated and have no slop. Replace them as necessary.
If your Jeep is lifted or has sagging or twisted springs, the drive shaft alignment may be off. Just couple of degrees of pinion misalignment can cause serious problem with the drive shaft. Also note that the alignment used for a double cardion shaft is different from that of a single tube with a single U joint at each end.
To isolate a drive shaft problem, try driving the Jeep with out the front drive shaft. The front drive shaft is easily removed and you can quickly tell if the vibes go away when the shaft is removed. To drive without the rear drive shaft, you will need some way to plug the transfer case if you have not modified it with a slip yoke eliminator. With the rear shaft removed and a suitable transmission plug in place, you can drive your Jeep using front wheel drive by placing the transfer case to the part time 4X4 setting.
Drive shat work can be expensive so it is often cheaper to swap in a used replacement rather than having yours fixed. Look for any warps or dents in the tube and replace the shaft if you find any problems.
Death wobble is normally a combination of factors. While stock Jeeps can have death wobble, it is much more common on lifted Jeeps. Bigger tires and the angle of the control arms exaggerate the already unstable inverted Y steering of the Cherokee.
Do not attempt to mask death wobble with a steering stabilizer. Replacing or adding a steering stabilizer may appear to correct the problem, but it will simply be masked until the source gets worse.
The most common source for death wobble is the track bar. Usually it wears at the frame end. This is a tie rod style joint with limited flexibility. If you have lifted your Jeep, you have already used up much of its range of motion and it will be easily damaged if the axle drops lower.
To test the track bar, place your hand on the axle end joint and have an assistant move the steering wheel back and forth. If you feel any play in the joint at all, the track bar needs to be replaced.
Note that many aftermarket track bars have poor life expectancy. I have found the ones from Crown Automotive to be well made and reasonably priced. Let me know if you need a quote on one.
Another common cause if the track bar is OK is wear in the control arm bushings. The axle end upper joint is sometimes damaged by oil dripping from the air box if blow by is an issue. The bushings are difficult to replace in the control arms them selves and it is sometimes cheaper to buy new control arm than to buy the two bushings.
Other things to check are the bolts that hold the steering box to the frame and slop in the pitman arm. Worn tie rod ends can also contribute to death wobble.
In extreme cases or where you have to drive a Jeep that is subject to death wobble, try altering the steering alignment a bit. Toe out will usually stop death wobble. It will wear the tires, but it will stop the wobble. I also fixed one by removing all the caster shims from the lower control arms.
Follow these guidelines and you will be driving a smooth running vehicle that can take you anywhere. Just realize it will take some attention to details to keep your Jeep running smooth.