Symptoms:

My 98 GMC Z71 truck was running fine till I put a lift kit and a set of bigger tires. What is happening now is the front is shimmy at 45 mph. I brought it back to the garage that did the conversion and they re-checked the tires and wheels for imbalance including the front suspension for any loose parts and all of these did not fix the problem. One thing I noticed though, when I put it on 4X4, the shaking seems to disappear. I am now thinking to remove this conversion and put the original suspension and tires. Any suggestion?

Tire Problem Advisor:

Since this problem only started after installing the converted suspension and bigger tires, I would disregard the electronic variable orifice power system. Instead I would concentrate on your suspension. When you put a bigger set of tires in your truck, the center of gravity of the vehicle also moved up and this must be addressed.

When the garage did the suspension lift conversion, did they add a stabilizer bar? This part will help keep your truck firm to the ground and can assist to offset the higher center of gravity. If you need to install the stabilizer bar, buy a heavy duty after market ones. Finally tell them to double check the run-out of the tires and wheels.

Notes:

When in doubt, bring your vehicle to authorized GMC dealer shop for a second opinion.

Above repair is only a recommendation and you do this at your own risk. Always have your vehicle align after replacing the tires to prevent repetition of the tire problem.