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Any cure for "death wobble"?

highrlr

highrlr

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Bismarck, ND
My truck is an '89 GMC jimmy. I have a D60 up front, with off road design crossover steering, a really beefy tie rod, PSC 2wheel drive steering box, weld on and bolt on steering braces, rebuilt kingpins, and all bearings. I am running 38x13R16 TSL's, and around 30-35 mph the death wobble is insane! Looks like the tires are going to fall off, and its like riding a bull on the inside! I would like to street drive my K5 more often, but it is almost impossible like this, not to mention embarising, and probably very hard on parts with this condition!

Does anyone have any tips for me, things to check, or things that may help? I realize swampers are not good on-road, but this is not a huge size, and would think it should be managable? I think I have heard of putting washers under the kingpin caps to put more preload on the kingpin spring, anyone have any info on that?

Also, I am running without a steering stabalizer. I am going to be doing hydro assist, so I do not want to install a stabalizer, since the ram should act as one.
 
Someone on here recently cured theres by welding a cross peice between the two pieces of the shackle maiking an "H". Other then that and the washers, most people will tell you to put a stabalizer on it.
 
Check your tire balance. I had it to the point people would not drive near me. I replaced steering stabilizers, did front end work and anything else I could do to stop it. I coincidentally put on another set of tires (bigger) and it magically went away.
 
You could try some extended shackles that will help tilt the rear of the leaf spring down a bit and add a little castor. There's also shims you can add between the spring pad and the spring.
 
Shimming the kingpin springs with a washer or two usually takes care of the problem. The simple fact is that the stock springs were designed to control a 31" street or all-terrain tire, not a 38" Swamper.

Now I will say that there could be other contributing factors, such as out of alignment , loose steering or suspension parts, unbalanced tires, etc... but try the shimming first.

I had almost the exact same setup as yours and had the death-wobble at the same speeds. With the existing kingpin springs (like the OEM from '77) I used two washers per side and it completely eliminated the death wobble. A couple of weeks later I put new springs and bushings/cones in the upper kingpins and went to just 1 washer per side and still no death wobble.
 
I'm curious on the real results of the springless arm design. Has anyone actually had death wobble and then swapped to the springless steering arm to find it gone?

I'd be curious to know if the bushings wear any faster, or whether they need adjustment after use.
 
I had the same problem. Rebuilt everything including KP, replaced all tire rods so on and so on. I bought new 33's (not 38's which would amplify any problems) and had the truck aligned. It came back out of castor spec and still had death wobble. I thought about the KP shims but never tried them as my KP were all new. I finally installed dual stabalizers and the problem hasn't been back. I think this is a band aid approach. The underlying problem is castor out of spec. If you can correct the castor you are better off. It will of course either entail some sort of shimming either longer shackles or a shim under the axle (not the right approach in my opinion if you want correct driveline angles) or cutting and rotating the tubes to achive correct castor and driveline angles.
 
Thanks for all the suggestions guys!

For the washers, should I just pull a cap and get washers that fit inside it? Does the inside diameter matter at all? I think I will try this for sure. I will probably also try welding a piece of steel in between my shackles.

As far as longer shackles, I have the off road design heavy duty shackles, which appeared to be longer than the stockers, but not posotive? Also, all bushings are new polyurethane, and I check all hardware a few times a year under there.

The tires are not balanced at all, I think that would be hopeless on a tire like this unless I ran the balancing powder? I have tried rotating them, and different air pressures, but nothing has helped. This truck is primarily a wheeler, like 99% of its life is in the dirt, but it is still driveable on-road, and If I can fix this issue, I will drive it on the street more often.
 
highrlr said:
Thanks for all the suggestions guys!

For the washers, should I just pull a cap and get washers that fit inside it? Does the inside diameter matter at all? I think I will try this for sure. .
Click to expand...
Just go to Lowes or Depot and get Fender washers. They are about 2 inches in diameter and a 16th of an inch thick.
Just pop the caps and stick 2 inside each cap, then bolt them back down........simple. You will like the result.
 
Chaddy said:
2 Fender washers under each cap. Thay are about 30 cents each
Click to expand...

this fixed my problem but the steering is kinda weird now, like its making the spring inside bind a little bit
 
It could be any of these things, I have tried the washers, stabilizers, shimd, and a bunch of other stuff, trying to fix it. None of them helped. When I had the death wobble, I had some used BFG's on there, and it seemed like it had just come on all of a sudden. They were balanced and all. I replaced them with bigger ones, and they have no balance. The thing runs straight without any death wobble. I am not saying it is the tires for sure, but see if you can borrow a set to try.
 
pseudomike said:
I had the same problem. Rebuilt everything including KP, replaced all tire rods so on and so on. I bought new 33's (not 38's which would amplify any problems) and had the truck aligned. It came back out of castor spec and still had death wobble. I thought about the KP shims but never tried them as my KP were all new. I finally installed dual stabalizers and the problem hasn't been back. I think this is a band aid approach. The underlying problem is castor out of spec. If you can correct the castor you are better off. It will of course either entail some sort of shimming either longer shackles or a shim under the axle (not the right approach in my opinion if you want correct driveline angles) or cutting and rotating the tubes to achive correct castor and driveline angles.
Click to expand...


Caster, if it's way out of whack could certainly contribute to DW but even if it's within spec you can certainly still have issues (I know from personal experience!)

There are many hypotheses about DW and what causes it, but there are a few universal truths I've realized after reading DW posts for several years.

1. DW is not specifically a tire wobbling issue, the entire front suspension is dancing around. That includes the leafsprings, shackles, etc. Sometimes it even includes the broken steering box area if that hasn't already been remedied.

2. I've NEVER seen a post complaining about DW from someone with either a front panhard bar setup (on a leafsprung suspension), or a multilink front suspension. If someone has a link to such a thing, I'd love to see it. The more I think about it, the more I'm convinced that soft leaf springs are a major contributor to DW, as they help to continue an oscillation that starts either from in inbalance in the tire, or from a shock entering the front suspension from some kind of bump or pothole in the road.

MY THEORY: If you can do something to control the side-to-side oscillations of the front leaf springs, you will cure DW. This is sometimes done with steering dampers, hydro-assist rams or panhard bars. Using washers in the steering arms can help attenuate the initial vibration which will make it less like to couple with the rest of the suspension and become a full-on DW event.


BTW -> It is possible to get carried away with washer shimming and go too far. Remember that the spring inside that cap needs to still have some small amount of movement when you're done, and if you stuff too many washers in there in your zeal to solve DW, you will bind-up the spring and your steering will suddenly become VERY stiff, and won't want to return-to-center on it's own. Ideally, you'd measure the compressed vs. uncompressed height of those springs and make sure that you don't add more washer thickness than the working range of those existing springs.

To be sure, DW is a terrifying experience... I'd suggest that you work through some of the tried-and-true suggestions first (washer trick, steering stabilizer, weld re-inforcements in front shackles, replace worn front spring bushings) Odds are good that you'll be able to mostly eliminate the issue.

:usaflag:
 
Jeep TJ's have 4 link suspension with a track bar (panhard bar) and I know death wobble is a problem for them as well. Usually caused by worn steering parts, tire balance, or incorrect caster.
 
abig84 said:
this fixed my problem but the steering is kinda weird now, like its making the spring inside bind a little bit
Click to expand...

Remove one washer from each side...

FWIW I totally agree with Greg on lateral movement being a huge contributor to DW. I had added two washers to each KP on my 60 and had no death wobble even with unbalanced 39.5" TSL's. This was with 4" Rancho springs.

I changed nothing as far as tires or front end parts but did get rid of the Rancho springs and installed some very flexy Alcan springs and longer front shackles. Instant violent death wobble that was very easy to trigger even at very low speeds. The only way to get rid of the DW was to intentionally put the king pin springs into bind. this got rid of the DW but made for some spooky steering and handling.

Before we get debates on caster, I measured caster and had 10 degrees. Shimmed to 8 degrees...no help. Shimmed to 12...no help.

Rene
 
I believe once the tires have experienced death wobble it screws them up. I believe that it messes up the cords and said tires will always be prone to dw.
 
I am with Greg and Rene on this one. Bigger tires than stock or softer springs will lead to death wobble on these trucks. Look at some of the trucks on leaf springs these days and they have a panhard bar or trackbar. I just made a panhard bar very similar to Dcubbs. After a few drives no death wobble. I did put the long springs up front and it had been terrible at in town speeds but normally after hitting a bump to set it in motion. I had replaced everything in the axle to get rid of it, no luck. With the new panhard seems to be cured. Best of luck.

Erik
 
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