Hi rthomas714. Welcome to the forum. Can you see the wobble, feel it, or both? If you can't see it, how do you know it's the left rear wheel?
If you can't see it, there are a few things to try to verify it's that wheel. Jack the rear end off the ground and run the engine in gear and watch the wheel. If it is true, look closely at the tire tread for any irregularities or bumps. That would indicate a broken belt and would make the seat shake but not the steering wheel.
If both the wheel and tire appear ok, use a dial indicator against the lip of the wheel while it's spinning slowly. Anything more than around.040" sideways run out should be investigated.
If you still don't find anything obvious, switch the two left side wheels front-to-rear and drive it to see if the symptom changes. If not, switch the two right side wheels.
Once you verify the wheel causing the problem, look for debris stuck on the back of the wheel where it mounts to the brake drum. This is most common with cast wheels, and less common with painted steel wheels. Also look for a chunk of corroded cast wheel that broke off and stuck to the brake drum. Use a wire brush to clean the drum and wheel. If the wheel is bent it will show up on the wheel balancer, but debris stuck on the wheel will often contact the brake drum but not the mounting hub on the wheel balancer. If nothing is found on the wheel, reinstall the lug nuts and run the engine in gear again and use the dial indicator on the mounting surface just outside of the studs. .010" run out there is quite a bit. Next, remove the brake drum and place the dial indicator against the axle flange while the engine is running in gear. You should find no run out at all there.
The most common cause of a wobble is a bent wheel, but you would have found that by now. Just as common is a broken tire belt, especially when they are near the end of their life. Next would be a bent or warped brake drum. Lots of hammering to remove a rusted-on drum, or use of a jaw-type puller can bend it, and improper tightening of the lug nuts is a real common way to warp it. The lug nuts must be tightened with a torque wrench for a number of reasons. A small person will be able to get them loose to change a flat tire, the nuts will be tight enough so the wheel doesn't come off, the nuts and studs won't be damaged, and most importantly, the clamping forces will be equal in all places. When the clamping forces are not even all the way around, it sets up the chance for warping to occur from the normal heating and cooling cycles.
Friday, May 14th, 2010 AT 8:02 PM