Death Wobble

My A108 has an intermittent violent shake that occurs at some magic combination of speed and road surface. It only happens above 45 MPH and doesn't matter if the van's loaded or empty. It clears when I slow back down below 45. I've replaced the shocks, front wheel bearings, and spring bushings but still have the problem. The tie rod ends look good but those are next on my list to replace. Given that a new drag link is so expensive is there a way to verify if it's worn before I take it off the van? Any ideas of what else could cause this type of resonant shake? - Thanks

Arnolt wrote:My A108 has an intermittent violent shake that occurs at some magic combination of speed and road surface. It only happens above 45 MPH and doesn't matter if the van's loaded or empty. It clears when I slow back down below 45. I've replaced the shocks, front wheel bearings, and spring bushings but still have the problem. The tie rod ends look good but those are next on my list to replace. Given that a new drag link is so expensive is there a way to verify if it's worn before I take it off the van? Any ideas of what else could cause this type of resonant shake? - Thanks

What exactly is shaking? Is the steering wheel vibrating back and forth, is it coming from the front suspension, from the rear (driveline), is the motor shaking, automatic or manual transmission, if you speed up faster when it starts does it get worse or better?

Check wheel alignment, king pins wore out, wheels balanced, tires have a weird wear pattern or flat spot.

1st thing, rock the steering wheel back and forth with 2 fingers, if it moves about a 1/2 inch or more, have someone look and see if pitman arm is moving while you rock it, if its not,  then problem is in steering box, you might be able to adjust it,,,,if pitman arm moves, then look at both ball joints on drag link, see if any of those move,,,,then check each tie rod ball joint, you are looking for looseness, you can try rocking the steering wheel harder but not hard enough to make tires turn and see if anything moves from the steering box all the way down to each steering knuckle. Another test, jack up each tire and push and pull it in and out, up and down and left and right to see if there is any looseness in wheel bearings, kingpins and all that steering linkage.

It feels like the suspension is hitting a resonance that goes away when I reduce speed. The whole van starts rotating about it's long (front to rear) axis. It first happened when I had a very heavy load in it but now it happens even when unloaded. It seem ok on an even road but if I hit bumps it sometimes will go into that bad rocking mode until I slow down. I haven't tried to speed up to see what happens. I'm also able to steer the van ok while it's doing it.

You got nothing to lose by switching tires front to back, you just might notice something out of place.

Your last post suggests that it isn't an issue if the road is smooth....It also suggests that the van rolls side to side rather than just having a severe tire shake.....
If I have that right, I believe what you are experiencing is called "bump steer"....
Other symptoms of bump steer include the steering wheel shuffling left and right over uneven road surfaces at 25-35 mph.....
Assuming you have already taken the suggestions from the other replies and made sure everything is tight and without steering slop, I have a couple of easy ways to diagnose bump steer:
1) Bounce the van up and down by jumping on the center of the front bumper.... Does the steering wheel turn left and right?.... That would be bump steer!
To further verify
2) Take note of the steering wheel position, even marking the hub2collar with a sharpie... next, jack the chassis squarely up in the front until the wheels almost lose contact with the ground.....Now, If the steering wheel is still in the same orientation.... no bump steer.....

If You've just got severe shaking or even a hopping wheel, it could be a tire coming apart, a bent rim, bad balance, or out of round wheel.... Usually you can isolate and verify by switching front wheels to see if a bounce or pull switches sides....

You will need to very carefully assess what is actually happening to get more specific advice!

be sure to check your u joint - at high speed it could start to wobble

im digging up some old history
but in 1974 my brother and i had the problem on a
1967 chevy van, we changed the king pins and
i dont recall ever having the problem again.

Another issue that hasn't come up in this thread is caster....
Does the van naturally go effortlessly straight if you let go of the wheel at 25 mph or do you have to fight to get to and stay centered and going straight......If it wants to go everywhere but straight, you likely don't have enough positive caster....
Others have suggested stuff that might be loose ( kingpins, steering ball ends, steering box adjustment) which should all be taken care of first.... also front wheel bearing condition and adjustment.....
Next would be wheel and tire condition and balance....
Then things like caster and bump steer
Good Luck!