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73-87 Chevy _ GMC Trucks => Brakes, Frame, Steering & Suspension => Topic started by: rwh1956 on August 16, 2009, 12:38:38 pm
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I've got a problem with my 1987 Suburban R10 ˝ ton. The shim height required under the upper control arm rods appears to be excessive at about 3/4” to 7/8”. This seems to apply too much leverage on the mounting bolts and the shims usually begin to fall out about three to four weeks after alignment. I've tried three different alignment shops with the same result. I'm pretty sure they aren't under torquing the control arm rod mounting nuts. I don't drive it hard, encounter no potholes or speed bumps over 10 to 15 MPH, have stock size tires and rims, and don't off road.
I vaguely remember when I bought it second hand back in the mid 90's, the upper control arm rods had offsets at the ends and the alignment shim stacks only had to be about 1/4” to 1/2” high. The upper control arm rods installed now are straight, just like all the ones I can currently find online. Could the old control arm rods with offsets be what I've heard referred to as “problem solvers”?
The only things I can think of to cause this are:
1)Front end of frame bent inward. (Except that would affect other mechanical alignments like the motor mounts (which are OK) and the frame cross members/braces (which are OK)).
2)Wrong length upper control arms. (I've seen a couple of message threads here that suggest something similar but that possibility was shot down.)
3)Front end mod kit. (Except everything looks pretty original. No dropped front end.)
4)Wrong spindles. (Except I doubt any other vehicles spindles would be so close to be able to “almost fit”.
5)Non GM generic replacement parts that are off spec (Could explain items 2 & 4.)
I'm at a loss on how to fix this. One alignment shop recommended spot welding the mounting bolt heads to stop their movement but that seems like a hack fix that will eventually backfire. I'd rather fix the real problem even if it costs more, not just band-aid it. I just can't determine the real problem. The only other thing I've thought of that may contribute to the loosening of the shims is that I always have to steer a hard right all the way to the stop as I pull into my driveway every day. While I don't slam it, I know there's a lot of force being applied to the front end to make that tight radius turn.