The service manual procedure is shown in the five drawings, but there's two warnings they didn't mention. The first one applies to all cars and trucks with air bags. They all use a "clock spring" under the steering wheel. That's a wound-up ribbon cable in a plastic housing. It can be wound up and unwound a total of just slightly more than the range of the steering system from full-left to full-right. It is imperative that you start with the steering system centered, then use some mechanical means to lock the steering wheel there. Be sure the new steering gear is centered when you connect the input shaft, then you can unlock the steering wheel. If you allow the steering wheel to rotate one or more turns either way in relation to the new steering gear, the ribbon cable is going to break. Either it will wind up too tight and snap off on one end as soon as you turn fully one way, or it is going to unwind too far and fold over on itself. That will happen multiple times, then it will break days or weeks later.
The second warning has to do only with GM front-wheel-drive cars. To my knowledge, this doesn't apply to any other car brand. To remove the steering gear, the procedure includes lowering the engine cross member. That is welded in place on Fords. Chrysler uses special bolts that force the cross member to go back to its original orientation upon reinstallation. GM doesn't do anything to insure that cross member goes back to its proper position, and if it is off-center by as little as 1/16", it will create the most miserable car to drive. You have to mark the location of the cross member in some way to insure it goes back together exactly the same way.
When the cross member is shifted to one side a little, it brings the lower control arms with it, and that changes the angle of the spindles. At first glance the basic alignment angle in question is "camber", meaning both front wheels will now be tipped more to one side than before. Camber alone causes a tire to pull to the side it's leaning. The initial goal is to have camber equal on both sides. That can be reajusted, but it doesn't solve the problem.
In this case with the cross member off-center, there is a more elusive underlying problem. That is unequal "steering axis inclination", (SAI). Basically that is seen as the angle of the struts, as viewed from in front of the car. No spec is given for that angle. All that is critical is it must be the same on both sides, typically within 0.2 degrees. Typical values are between 28 and 32 degrees. SAI is measured automatically by all alignment computers, but we rarely look at it unless we've been told there is some reason to do so, or when we're evaluating crash damage repairs.
When we don't know there is a reason to check SAI, we typically see the unequal camber and just adjust that. The camber numbers can look perfect on the alignment computer, but if SAI was overlooked and is unequal, the car will have no "predictability". That means it can dart either way unexpectedly from just the tiniest of bumps in the road. Steering response will not react the way you expect it to. You'll be a nervous wreck from just trying to drive it to the alignment shop.
SAI is fairly easy to adjust once the car is on the alignment rack. The cross member bolts are loosened, then the cradle can be forced to one side with a long pry bar. Camber will have to be checked and / or readjusted after SAI is corrected.
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Tuesday, December 31st, 2019 AT 11:41 AM
