2004 Pontiac Bonneville motion in car

  • 160,000 MILES

Car sways after hitting bumps. Car moves from side to side like a rollercoster, but feels fine during driving strait on the road. What could cause this. Could this be a real suspension problem, or could this be a steering problem? I kicked all four tires, and there didnt see any kind of movement with the wheels when the car wasn't moving.

Do you
have the same problem?
Tuesday, June 18th, 2013 AT 4:56 PM

1 Reply


Kicked the tires and nothing moved? That could be true of a wheel that's ready to fall off. We use pry bars to identify worn parts when the car is up on a hoist.

What you're describing can only happen on GM front-wheel-drive cars, and after the engine cradle was removed to service the engine or transmission. It is critical that it be reinstalled in the exact orientation as when it came out. When the cradle is reinstalled off-center that changes "steering axis inclination", (SAI), and "camber". Camber is the tilt in or out of the wheel on top as viewed from the front of the car. That is one of the basic angles set during an alignment, and while that can be corrected after the cradle is reinstalled, it will not correct SAI. You need to have the alignment checked and attention must be paid to the SAI on both wheels. All alignment computers measure SAI automatically but alignment mechanics rarely bother to look at it unless they have a reason to suspect it's causing a problem. There is no spec given for SAI. What is important is both sides must be exactly the same, within 0.2 degrees.

When SAI is unequal the car will dart from side to side as the suspension goes up and down and when the car hits bumps.

Was this
Tuesday, June 18th, 2013 AT 11:58 PM

Please login or register to post a reply.

Recommended Guides