Another D60 Death Wobble thread (but slightly different)

[Leadfoot]

My buddy has a 1985 K30 Dually plow truck with dump body. This past year he developed pulsing while braking and death wobble. About 8 months ago he put on new Calipers, Rotors, and pads which cured the brake pulsing but when he put on the 9.5' plow, anything over 30 mph and a bump equalled no control over the truck (death wobble). He installed new sway bar bushings as those were shot, and he put on brand new leaf springs and new hardware. I had him install a new drag link and adjuster, new tie rod ends and adjuster, and new steering stabilizer (little/no effect). I then ordered him for Christmas a complete front end rebuild kit (new upper/lower kinpins and associated hardware), new axle unjoints, new spindle bearings and seals, new inner/outter bearings and races on the hub, and all associated seals. We put those in a few weeks ago and everything seemed fine. He called me to tell me today that it came back after hitting a bump with the plow on. He said it was just as violent, but not as easy to bring about or as often.

I have a rebuilt steering box from Matt at West Texas that I'm going to put on, but I don't know if that will help (although it can't hurt). This truck is STOCK as stock can get. No offroading, factory wheels, tires, gears, motor, tranny, etc. and Everything from leaf springs to seals are all new in the front end.

Just to be safe, I am going to recheck all fasteners, install the rebuilt steering box, and have him get it aligned and tires balanced, but does anyone have any ideas if that does not work??

I don't like the thought of using washers on the kingpins especially on a STOCK truck that was COMPLETELY rebuilt, but if I have to I will (as death wobble is not acceptable). I did several searches and weeding through the posts I see that fender washers are what most use, but could not get a consensus on thickness or diameter. I saw one person post about a washer that was 2" OD, is that the ideal size?

Thanks in advance.

 

[scotto0609]

Try swapping tires front to back first. The previous death wobbles might have ruined the tires?

 

[camok5]

This is what I have learned about death wobble over the past few years. Death wobble is caused by bad harmonics in the front end, kinda like a tunning fork, that is why its set off by so many different things. All it takes is ons little thing out of wack to set it off again this is also why there are so many different suggestion on how to fix the problem (its caused by different things for different front ends). I have never heard of a cure other than getting lucky on figuring out whats causing it in your front end. Most people just band aid the problem by putting a new steering stabilizer on or running hydro assist, both seem to work because it slows down the bad harmonics to the point you cant feel the death wobble anymore (kinda like when put your hand around the tunning fork to get it to stop). Also dont think that its just dana 60s and dana 44s that have the problem either because a couple of my work trucks both 2wd ford f450 also have bad death wobble. I could be completely wrong about this but its the best explanation I have heard so far.

 

[b454rat]

Hmm, my 79 dually K30 does the same thing without the plow. With the plow on it drives great, take it off and hit 30-40 mph, hang on.

The tires are a good idea, gonna try that I mine. Does it have full time hubs??

Only other thing that I can think of is pinion or castor (??) angle.

When I had my 89, it first had a GM 60, then swapped it out for a HP60. Both axles were completely rebuilt. In fact, the HP60 had the GM60 outers on it, knuckles out. With the GM60 (running 40" boggers), hitting a bump the right way would get DW. Made it a pain to drive sometimes. But when I switched to the HP60, NEVER got it again. The only thing that got changed was the axle itself, still had the GM outers and 40" boggers, and they weren't balanced.

I noticed on a buddy's truck (HP60), that his crossover arm was about flat, parrellal with the ground, while mine (GM 60) was tilted back, the front where the TRE bolted on was higher than the rear part, where it bolted on the knuckle.

I'm gonna put some small shims on my 79, hopefully that is the cause, everything else is good and solid....

 

[protechk5]

X2 on the tires, also did he get the alignment checked out? Maybe even try new bushing in the springs and spring hangers, when those wear out it gives side to side movement of the axle.