Mechanics

CHEVROLET SILVERADO WHEEL PROBLEM

1999 Chevrolet Silverado • 188,000 miles

I have a '99 Silverado 1500 with a 4.3L V-6. It picked up a problem recently that's been stumping me. Occassionally, and for no reason I can sort out, it starts to shimmy badly. This behavior has come about at several speeds. Sometimes just cruising down the road at 35-45 it starts to shimmy and wobble and the steering wheel shakes as if a wheel is horribly out of balance. Other times this occurs at highway speeds - it's noticeable and alarming. The problem can last a long while; othertimes the symptoms disappear in a few seconds. The first time it happened I thought I had a flat or was about to lose a wheel.

I've checked several things and came up empty. No delamination in the tires and nothing out of round, but just to be sure I had the wheels balanced and rotated - the balance was spot on when checked. Alignment is good. Did those things, but the symptoms continued. The vehicle has 188,000 so I put in on the lift and checked the front-end. The steering rack has a very slight amount of play and the hub bearings have a very small amount of play too - I'll get after those, but they're not causing this intermittent problem. Everything else is tight. Shocks are fine, brakes are fine, I checked the rear-end as well - everything is straight and true. Air pressure is set correctly. I checked the driveshaft for runout and play - that's not the problem. The truck has never been in an accident and nothing seems misaligned.

The truck drives like a new truck most of the time, then suddenly, on a smooth road, it starts wobbling around. I'm starting to believe the problem might lie under the hood. I had a problem some time back with misfiring and the truck bucking - this turned out to be a worn distributor. A new distributor, rotor and wiring solved that problem. But these symptoms are not similar - this is not a bucking problem; the entire vehicle starts to shimmy and wobble with the steering wheel vibrating back and forth. It's hard to tell, but I cannot detect any misfiring or rough running in the engine when these symptoms appear and I have no 'check engine' warnings.

Are there any engine/transmission/drivetrain related issues that could cause intermittent symptoms that feel like an out of balance condition?

A few other facts:
- I have noticed the truck is a little down on power lately
- The fuel economy has dropped off - I used to do around 20, now I'm down to 16mph highway
- (Very) slightly rough idle

Thanks for any advice you can give!
Avatar
Guest
January 22, 2013.



Check out the related content below while we wait for the question to be answered by a professional mechanic.