Question: If I get a 4.5-inch lift and 2-inch coil spacers on my '89 Jeep Cherokee, will I have to get new upper control arms too, or just lower ones?
Cody Hansen
via fourwheeler.com
Answer: While it can be done-and I am sure some people have done it-I don't think that using a 4.5-inch lift and 2-inch spacers is a good idea for several reasons. A lot of people will stay with the stock arms with a 3- to 4-inch lift for mild four-wheeling. However, the aftermarket provides stronger tubular arms because they are a lot stronger and resist bending like the stock arms will over time.
Another problem is going to be ride quality. With that much lift and "short," stock-length control arms, the angle of the arms is going to be very steep. Take a minute to make a simple drawing of the control arms in relationship to the ground in stock ride height. Note how they are parallel to the ground. Now raise the body up 4.5 inches and note the angle of the arms. Pretty darn steep. Take your compass, putting one end at the arm attachment point on the unibody frame and the other on where the wheel would be. Draw the arc that the wheel will now travel upward in. You can easily see that the wheel has to move forward as it goes upward. When the vehicle is going forward and you hit an obstacle, the wheel also has to go forward when the suspension tries to compress. Talk about forcing something in the wrong direction! Not only does this greatly affect ride quality, it also puts a lot of stress on all the mounting points.
My personal opinion is that 3 to 3.5 inches is just about maximum lift height with stock-length arms. Any more lift than this, and you had better look into a "long-arm" suspension kit. The long control arms reduce the operational angle so that it's not perfect, but much better than the stock arms with a given amount of lift, and allows so much better articulation without putting stress on the mounting points.
Question: I bought a '98 Jeep TJ used with a four-banger and automatic. It now has a vibration between 40 and 50 mph. We changed the tires because it had some cheap Wally World tires, and also changed the U-joints on the rear. A mechanic checked it, but could not find nothing. Could the driveshaft be out of balance? If so, would a centramatic balancer help? Or do you know of any problems that the Jeep could have to cause a vibration? If you let up, or give it gas, it will quit for a while.
Barry Bivens
Leoma, TN
Answer: Vibrations can be hard to identify, especially with the limited information you have given me. While you changed tires, you didn't say if you changed rims, but hopefully the technician who balanced your tires would have mentioned if the wheels were bent or if he had difficulties balancing them.
You also failed to say if the Jeep had any type of lift on it or not. A suspension lift kit will change the driveshaft angles, and unless corrected, these can very much cause vibrations. Depending on the amount of lift, you could simply lower the transfer case to obtain the proper angle, or better yet, buy one of the slip-joint eliminator kits that are on the market. This will gain you several inches of driveshaft length, which in turn will reduce the driveline angle. The problem with dropping the transfer case is that it then puts the front driveshaft at the wrong angle and you could get some vibrations from it.
The vibration could also be coming from one of the front axleshaft U-joints or a bad wheel bearing in one of the front hub assemblies. Even a bad bearing in the front or rear differential can cause a vibration.