yo,
Wobble Diagnosis
Source: by Carl J at
http://web.archive.org/web/20090402131611/http://www.jantz4x4.com/deathwobbles.php
Here is Carl's article in full for posterity.
..."...Death wobbles are caused by two main factors; loose or incorrect front-end alignment parts and large out of round or imbalanced tires. Assuming your tires are still in balance, not full of dirt clods and you don't have a bent rim, here is what I look for when experiencing "death wobbles" on the following rigs.
*Note: Always have your rig on level ground with motor off prior to doing any vehicle inspection!
One thing to remember - a steering stabilizer or two may get rid of the death wobbles, but will not fix the problem that is causing the wobbles. I have personally run 44" tires on all my rigs for the past 21 years and have been able to run without a steering stabilizer once the root cause was corrected.
Of course if you need any of the following suggested parts we will be glad to provide them for you. Read on to see how to diagnose: coil sprung, leaf sprung, and independent front suspensions.
Bronco's & Ford ½ tons
I'm going to assume that the rig by this time has already had someone install the 14 piece urethane bushing kit in the front end trying to remedy some of the death wobbles. If not install a kit and look for the following as you do it.
1st thing on early broncos is to get a friend to rock the wheel (with the motor off) back and forth about a 1/3rd of a turn. Look at the track rod from the frame to the axle (mounted just behind the steering box) Are the bolts holding the track-rod mounting bracket loose? Is the bushing in either end of the track rod worn? Are the holes for the track rod bolts in good shape, or are they egg shaped so that even when the bolts are tight they can be forced back and forth?
FIX --> To correct this quick and easy, weld a washer that fits tight on the bolt to the front side of the bracket and weld the nut to the back side. Is the large bolt in the front end housing wobbling with the steering wheel? FIX --> by welding the bolt head back to bracket, or buy a tapered bolt kit, (for cast mountings) and install.
2nd Check the steering box bolts, are they loose? Look for chipped paint or rust rings around the bolts, better yet just go ahead and retorque them now, you will probably get a full turn out of them. If they do not tighten to a firm stop... FIX by installing new solid sleeves between frame rails. The early Bronco's had sleeves in the frame but they were a split design and crush open after awhile.
3rd Tighten the pitman arm nut; you can usually get ½ a turn out of it.
MIESK5 NOTE; BE VERY CAREFUL HERE; see Steve83's Pre-load Adjustment, All Bronco & Ford, mid-70s to 00 (
http://www.supermotors.net/vehicles/registry/media/513527)..
and his Steering Troubleshooting
Source: by Steve83 (Steve, That dirty old truck) at SuperMotors.net (
http://www.supermotors.net/vehicles/registry/media/513527)
*Note some aftermarket drop down arms will slip up the splines far enough that the lock washer will bottom out on the shoulder of the pitman shaft and you will think it tight but it is not, so you have to lathe a special spacer to push the arm father up the splines with out bottoming out the nut.
4th Check all the tie rod ends for endplay. With the wheel-rocking trick, start at the pitman arm, there should be no motion between the arm and the drag link, or the drag link to the tie rod, or the tire rod to the steering arms. Replace and align as required.
5th Place the front end on jack stands, then grasp the tire at top and bottom and alternately pull and push the tires with opposite hands. If the tire moves more than 1/16" either the upper and lower ball joints need to be replaced or the wheel bearings need adjustment, or in a worse case scenario the spindle is cracking or the spindle bolts are lose.
Leaf spring vehicles
My 1st death wobbles occurred when I was about 16 years old and decided to lift my Scout with 12” long shackles. I bought 2 kits used for raising the back of a Mustang and in a couple of hours I had the tallest Scout in town. My 1st drive was quite interesting; any speed over 30 miles per hour and it was all over the road. After talking with several experts it was decided that my caster had changed. At the time I did not have the $14 bucks for a couple of degree shims and so with 16 year old logic decided that since the rig had leaf springs under the axles all the weight of the vehicle was carried through the U bolts and that a set of wooden shims would not carry any weight but would tilt the front end in the correct direction. After several practice splits with a sharp hatchet and some carving with a knife I had a set that looked about what I needed. I loosened the U-bolts placed in the shims and sure enough it drove fairly good again. Unfortunately about 100 miles from home a week later the wood splintered and came out. I did not have a wrench with me to tighten up the bolts so I had to drive at 15 miles per hour all the way home because anything more produced death wobble. So……
1ST thing to check for is loose U bolts and then have a friend rock the wheel back and forth about 1/3 of turn while you observe the following steering components.
2nd I check for loose spring bushings
3rd look for loose tie rod ends & drag link ends.
4th Check that the steering box mount to the frame is solid. Jeeps are notorious for cracking these mounts and an after market steering brace should be added to any vehicle you plan on taking off road. Have a friend rock the wheel back and forth about 1/3 of turn while you observe the box and related steering components.
5th Place the front end on jack stands, then grasp the tire at top and bottom and alternately pull and push the tires with opposite hands. If the tire moves more than 1/16" either the upper and lower ball joints need to be replaced or the wheel bearings need adjustment, or in a worse case scenario the spindle is cracking or the spindle bolts are lose.
.
Note: Although it takes a little longer, I have seen the cast aluminum shims eventually break apart just like my wooden shims did. I now make steel shims to fit all applications.
Independent Front Suspensions
Look for all the loose stuff mentioned above and look for loose bolts holding the A-arms onto the frame and or loose center pivot bushings.
Finding loose parts is best accomplished by having a friend (MOTOR OFF!) Rock the steering wheel back and forth about a 1/3 of a turn at 1 second intervals with the vehicle sitting on the ground, in park or 1st gear with Emergency brake set, while you crawl underneath and check for relative motion on every suspension connection and steering component..."
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