Q: I have a problem with my 2004 Jeep Grand Cherokee with 154,000 miles. While driving at speeds greater than 45 miles per hour I noticed a problem in ride smoothness. My tires are fairly new, properly inflated, balanced, and alignment is proper. I replaced all four shocks a couple of months ago. No unusual wear patterns on the tires. Initially, the problem started out when I take my foot off the gas at freeway speeds. During that abrupt deceleration the vehicle seems to "float" and "shimmy." When I resume acceleration the vehicle "shimmies" and "floats" again. Any roughness on the highway surface, crosswinds or following semitrailers cause these symptoms. There seems to be a bit of play in the steering but no pull on the steering wheel. I have been to a Jeep dealership and a reputable private service center — both can replicate the problem but neither can find anything abnormal. Please help.
A: With 11 years and over 150,000 miles on the vehicle, two likely possibilities exist — crash damage or worn parts. Even with new shocks, rubber bushings in control arms, stabilizers and track bars, ball joints, tie-rod ends, steering gear and the like may be worn enough to allow the vibration or shimmy to go undampened.
Residual crash damage, perhaps unknown or not identified previously — like a bent steering sector shaft or pitman arm — can allow excess movement in the steering that creates a shimmy or vibration. Also, don't overlook the tires — a belt shift or separation can cause this type of behavior.
Speaking of steering, the steering linkage on your Jeep features a shock absorber-like steering dampener to help control steering oscillations. At this age and mileage, this may be the primary suspect.
Q: We have had endless tire issues for years with our 2006 Pontiac Grand Prix. The tire was flat yet again tonight and when we brought it to a tire dealer to be repaired, both of the mechanics said "you don't want to do that" when we suggested radial inner tubes. However, we did not get a clear explanation for their disapproval. How do radial inner tubes solve tire-pressure issues?
A: By holding air. As I said in my column, I rate the installation of radial inner tubes as a last resort to tire bead-to-rim air leaks. If cleaning, sanding, polishing, painting and/or sealing the bead area of the rim does not stop the air leaks, a radial tire inner tube might be the only answer short of replacing the wheel. It's very important to differentiate between a standard inner tube and radial tire inner tube. Radial inner tubes are not available for all sizes of wheels/tires. The potential issue with installing radial inner tubes on a tubeless tire is pinching and chafing of the inner tube, eventually causing the tube to fail and the tire to go flat. A correct-sized radial inner tube is less likely to suffer this issue.
Q: Regarding cellphone use while driving, I am told there are several apps available that a phone user can download to disable his phone while driving should the individual choose to do so. Check it out.
A: Every cellphone has a built in "app" to prevent use while driving. It's the "off" button. So does the driver — just don't use the cellphone while driving.
