Mechanics

REPLACE LOWER CONTROL ARM?

2001 Nissan Frontier • 100,000 miles

How do I Change a lower control arm with torsion bar suspension?
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Guest
February 2, 2013.




You have torsion bar springs. Replacing the control arm is pretty involved, and it's a lot worse if the vehicle isn't up on a hoist. Your best bet is to get the manufacturer's service manual and read through the instructions to see if you want to attempt the job. The truck must be supported solidly on jack stands under the frame. First you must unwind the adjusting bolt to remove all the wound-up tension on the torsion bar. I can't tell you how to remove that bar because I never did one, but it usually involves removing a wire clip or a bolt, then sliding the bar rearward out of the control arm. On some vehicles the bar can't be slid back. You have to unbolt the control arm, pull it to the side, then pull it off the torsion bar.

The ball joint stud must be separated from the spindle and the bottom of the shock absorber must unbolted. Remove the two pivot bolts, then pry and wiggle to remove the arm. One thing most do-it-yourselfers and inexperienced mechanics mess up is tightening those pivot bolts while the truck is jacked up and they have easy access to them. The suspension will be hanging down. If you tighten the pivot bolts that way, the rubber bushings will be clamped in that orientation, then when you set the truck on the wheels, the control arm will go up to its normal position and those bushings will be in a permanent twist. That will seriously shorten their life because they will be twisting much further than they're designed for as you go up and down on the road. Leave the two bolts a little loose, bounce the truck a few times or drive it a little, then crawl underneath and tighten them. You'll need to adjust the ride height before you tighten those bolts. Running that bolt up is rather hard with the vehicle weight on it. You will be lifting the corner of the truck. It's easiest to count the number of turn it takes to lower it, then run it back up the same number before you take it off the jack stands.

Measure the ride height too. All tire and alignment shops have small books that show every car and truck, where to take the measurements, and what they should be. To get started, raise the side you're working on until it matches the other side and the truck sits level. The nice thing about torsion bars is they are easily adjustable. Alignment mechanics get awfully picky about correcting ride height because the numbers on the alignment computer can be perfectly in specs, but you'll still get horrendous tire wear if ride height is wrong, due the change in the geometry of the suspension system and the arcs the control arms go through as you bounce down the road.

When you take it in for the alignment, when the mechanic sees the new control arm, or when you tell him it was just replaced, he will likely loosen the pivot bolts on the drive-on hoist and retighten them out of habit and to be sure the bushings aren't twisted.

Caradiodoc
Feb 2, 2013.


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