Posted by Keith in Washington on Monday, March 13, 2006 at 1:10PM :
In Reply to: Wheel Shimmy posted by Pat Hazel on Sunday, March 12, 2006 at 11:49PM :
I have seen this shimmy at about 30 to 35 in many ff PW. It really seems to be a characteristic of them. It can be gotten rid of or greatly reduced. It is often caused by a tire being out of balance or a bent or out of round rim. It is made worse by worn or loose steering components or axle bearings. Currently, this problem is basically non-existant on both of my trucks, but it has taken a lot of work.
The previous replies to you are right on. It took replacing the following to fix it on my trucks.
Replace wheel bearings
Replace king pin bearings
Replace cups in drag link (be sure to check to see if the balls on the steering arm or pitman arm are badly worn. I replaced both on my ff PW)
Adjust steering box
Replace spring bushings
Replace tie rod ends
Make sure that the steering arm to hub bolts are tight (mine have backed off once)
The king pin and axle bearing are usually easy to tell if they are loose or bad as are the drag link ends.
The tie rod ends are not as easy to tell if they are bad. I felt no slop in my tie rod ends but I replaced them because of what I learned with my Suburban. When I had them out I could move the ball very easy by hand with very minor slop. When I installed the new ones it immediately solved two problems. 1) A slight shimmy at 35 MPH 2) The truck no longer pulled to the right when I hit the brakes (I fought this "brake" problem for years and learned what the problem was when I put new tie rod ends in my Suburban which had the same problem).
You can not believe what new spring bushings and pins can do. Metal against metal even when lubed results in wear. Any slop in the spring busings allows the whole front end to vibrate/shimmy. Any imbalance of a tire or a vibration started by hitting a hole in the road can set the whole front end shaking which you will feel through the steering wheel. IT is not cheap to do but well worth it.
What did I get when I fixed everything. My WC53 will travel at 65 to 70 MPH (V8 with 4.89 gears)with absolutely no wander or vibration. I can let go of the steering wheel and the truck continues straight for a long time. I have a set of 9.00 X 16 Michelin XL tires on combat rims on it that never have been balanced. I am at basically the same point with my ff PW except I have a slightly bent rim that causes some vibration.