Help with Death Shake/Wobble

[deathrowdave]

I agree just rebuilt a Dodge with a Dana Axle new pins and bushings / or ball joints will more than likely repair the problem . Mine were shot hard to determine until removed for repairs.

 

[rickf]

I agree just rebuilt a Dodge with a Dana Axle new pins and bushings / or ball joints will more than likely repair the problem . Mine were shot hard to determine until removed for repairs.

Just so you know, king pins and ball joints are different setups.

 

[Keith_J]

After looking over the design intent of the upper kingpin joint and considering the age of the truck, I ordered new bushings and springs for my 1031. The reason for the spring is to keep the bushing under limited compression so it won't distort/shatter with excessive load. But when the spring compresses, the force keeping the bushing on the kingpin decreases, allowing wobble. Harmonic motion of this type is a mass-spring system, the natural frequency of the system depends on both the mass and spring rate. Lowering the spring rate lowers the frequency and increases the amplitude to where gyroscopic stability of the wheel cannot damp oscillation. Bam, you get death wobble.

 

[rickf]

Engineers! How do you figure when the spring compresses it decreases force on the bushing? It is bearing directly on the bushing. The upper king pin is slightly tapered towards the top and the only force on that joint is lateral so as it gets lateral force the bushing will try to ride up the pin, it is prevented from doing this by the preloaded spring. Any movement up will only increase the force down exerted by the spring. Now, if the bushing is cracked or worn or the spring has lost tension then you have the death wobble situation. Once that oscillation starts it will do a lot of damage to the bushings in short order. You also have to figure in the roller bearing on the bottom of the joint, I have seen these rust solid from lack of grease. There are also preload shims on the lower that need to be set.

Rick

 

[ODdave]

Just throwing this out there..... What about death shake on a ball joint truck? With new ball joints? Explain that.

 

[rickf]

All of the same things pertain except it is much easier to detect worn ball joints. Jack under the axle and put a pry bar under the tire and pry up and down, if there is play the lower ball joint is bad. Grab the top of the tire and push in and out, if you have play the upper is bad. Ball joints got a bad rep for a long while but they have gotten them sorted out and they are every bit as strong as the king pins now. Changing them is a different story!

 

[Keith_J]

Engineers! How do you figure when the spring compresses it decreases force on the bushing? It is bearing directly on the bushing. The upper king pin is slightly tapered towards the top and the only force on that joint is lateral so as it gets lateral force the bushing will try to ride up the pin, it is prevented from doing this by the preloaded spring. Any movement up will only increase the force down exerted by the spring. Now, if the bushing is cracked or worn or the spring has lost tension then you have the death wobble situation. Once that oscillation starts it will do a lot of damage to the bushings in short order. You also have to figure in the roller bearing on the bottom of the joint, I have seen these rust solid from lack of grease. There are also preload shims on the lower that need to be set.

Rick

I was talking about set in the spring over time. What I have seen from worn bushing-springs is set on the springs. Wear will also decrease the spring force. Of course damage to the bushing will also decrease the load plus induce play.

 

[ODdave]

All of the same things pertain except it is much easier to detect worn ball joints. Jack under the axle and put a pry bar under the tire and pry up and down, if there is play the lower ball joint is bad. Grab the top of the tire and push in and out, if you have play the upper is bad. Ball joints got a bad rep for a long while but they have gotten them sorted out and they are every bit as strong as the king pins now. Changing them is a different story!

I said with new / tight ball joints.

 

[rickf]

And I said, "All of the same things pertain". Death wobble is most of the time caused by something other than ball joints or king pins. It is usually found in the steering system somewhere. One thing that has not been mentioned is wheel bearings and spindles. I used to own a 4X4 shop so I saw a lot of damaged front ends, I have seen death wobble caused by something as small as a loose wheel bearing. One thing that used to pop up a lot was worn spindles. These guys were in the mud every weekend and a lot of the time the front end did not get cleaned out every week. Once a bearing dries out and spins the race on the spindle then that spindle is on it's way out. The bearing will never fit snug again. You can peen the spindle with a pin punch and it will hold for a bit but only enough to tell you if that was the problem.

Rick

 

[bimota]

Track bar replacement - who has the part number handy - were there several types used on CUCVs?

 

[bimota]

Ok, time to start a new thread for experts to really get this right - to much miss information - could lead to serious damage and injury. Please refer to new thread I'll start this morning - "Experts input on CUCV death wobble, front end violent shimmy - serious only"

 

[rickf]

You are going to get all the same "EXPERTS" as any other thread. That is why I no longer post on here about this problem. By the way, there is no track bar on a CUCV.

 

[bimota]

CUCV Death wobble solved - key steps to avoid wasted time and money

Ok, it appears that my recent “expert” post was deleted - see what happens when some of you start swearing at me, let's keep it to the learning - regardless of how much you want to swear.

Key lessons learned on CUCV mid 80's with Dana 60 front end death wobble:
Death wobble is a very specific and violent front end shaking at 20-30mph on bumpy roads with an otherwise perfectly driving truck. This is a very specific and identifiable issue - this is not a mild shimmy or an irritation - this shacking is so violent that is requires bringing the truck to a complete stop prior to continuing.

1. New king pin springs is key, even good looking spring may be dysfunctional - see photos - this is a 30 minute job and the kit I bought was $28. Attached are photos of the "good" springs I apparently had - see the difference yourself.
2. Steering dampener - change that - this is a $40 -$60 part and 10 minutes to change
3. Front wheels balanced well - some have gone as far as beeds inside the wheel to get dynamic balancing.
That's it - it fixes the problem and makes the truck wonderful to drive again.

Most shops no longer have the skills for these front ends and they will cost you money - If you have money then take it to the shop. Otherwise follow above.

 

[poppop]

After reading this thread I took apart the front axle on my 83 chevy one ton 4x4 which we had not driven much in a couple years because of how bad the front end shook. I did not know what else to do after changing the tires and that did no good. It was completely worn out with plastic bushings busted. My kits were $82.00 but included the bottom bearing, new top plate, top pin and gaskets. NAPA wanted $125.00 a wheel for theirs.

 

[MakersTeleMark]

You owe me $100. Straight up. I can get the mods to pull out the archived thread.

Don't welch.

 

[wayne pick]

Good luck with that brother, as per post #53, he made it sound like he made his own diagnosis. The question was answered by yourself early in the thread, and others afterword.

 

[rickf]

Ok, it appears that my recent “expert” post was deleted - see what happens when some of you start swearing at me, let's keep it to the learning - regardless of how much you want to swear.

Key lessons learned on CUCV mid 80's with Dana 60 front end death wobble:
Death wobble is a very specific and violent front end shaking at 20-30mph on bumpy roads with an otherwise perfectly driving truck. This is a very specific and identifiable issue - this is not a mild shimmy or an irritation - this shacking is so violent that is requires bringing the truck to a complete stop prior to continuing.

1. New king pin springs is key, even good looking spring may be dysfunctionalView attachment 414448View attachment 414449 - see photos - this is a 30 minute job and the kit I bought was $28. Attached are photos of the "good" springs I apparently had - see the difference yourself.
2. Steering dampener - change that - this is a $40 -$60 part and 10 minutes to change
3. Front wheels balanced well - some have gone as far as beeds inside the wheel to get dynamic balancing.
That's it - it fixes the problem and makes the truck wonderful to drive again.

Most shops no longer have the skills for these front ends and they will cost you money - If you have money then take it to the shop. Otherwise follow above.

That is fine as long as the bearing on the bottom is not bad or if either pin is not scored and worn. I have had to replace the upper king pin on several customers trucks.

 

[lindyp38]

please tell me how u replaced the sway bar bushings....as im having a really tough time pressing them in......thanks mario

 

[rickf]

CUCV's do not have sway bars other than maybe the dual wheel models. Those I am not sure but if they do the bushings are no big deal. I am thinking you mean something else? Maybe the spring bushings? If the spring bushings you will need a socket that bears against the metal sleeve part of the bushing and a hydraulic press. Most people go with aftermarket urethane bushings which are two piece and install by hand.

 

[319]

please tell me how u replaced the sway bar bushings....as im having a really tough time pressing them in......thanks mario

Trash the one piece bushings and get the two piece urethane bushings.