"death wobble".............chassis issue?

[Freightrain]

I'm taking it in tomorrow afternoon for a look-see. Hopefully they will find something drastic and I can get this nightmare over with. It's first come, so I'm going to have to take my chances if they aren't busy.

If things continue in a bad way, I'll give you a call. I do agree, it does feel like a tire issue up front. Thinking back from last weekend, while taking a slow corner, I can remember the wheel still slowly shaking in my hands as it pulled around the corner. That tells me it's front tires.

[Freightrain]

Back to square one. Tire shop found nothing wrong with the tires. Both run dead true and even. We did dismount each front tire and check for balance stuff. There was "Counteract" in them and it was all loose and doing it's job.

I priced new Firestones($863 mounted) for the front. Ouch.

Did drive it a short hop up the freeway, but had a hard time keeping it under 55 to see how it was. 3 lanes of madhouse drivers, so I ran 65-70 with everyone else and got back off and went home. I know it still has some issues, need some open highway to play around on.

[Mike]

Larry, Have you tried off setting the weight on the problem side of the truck yet? Ya need to get a BIG MOMMA to ride with ya on the problem side and that will off set the weight enough to make the ride smooth as silk again. I always thought if your not bounceing then your not having any fun. I usually let my g/f ride in the same seat with me, which makes it more fun.

mike

[Freightrain]

Well, I did a bit more investigating tonight. I checked king pins and tie rod ends, but I looked a bit closer. I just felt the tie rod ends, but rolling it around. Seemed snug enough? Wrong. Jacked on the tie rod end and it's loose(both sides). Guess that's the reason for the wobble. Going to call Barry tomorrow and check on parts.

[Rob]

Well, I did a bit more investigating tonight. I checked king pins and tie rod ends, but I looked a bit closer. I just felt the tie rod ends, but rolling it around. Seemed snug enough? Wrong. Jacked on the tie rod end and it's loose(both sides). Guess that's the reason for the wobble. Going to call Barry tomorrow and check on parts.

I can't seem to trust my own judgement on tie rod ends. I have a large ball joint press that I'd bent from abuse pushing out some ball joints on a large GM car years ago. I made a spacer to push against the bottom of the rod end, and the forcing screw. By using a wrench to advance to pressure screw, you watch the rod end compress if it is bad.

Rob

[swjr]

I see several issues here .... I agree the tyres need warmed then measured and the interior of those tyres need to be cleaned very good and rebalanced. Tyres with broken belts will sometimes cause the axles to do this, even make them hop like a rabbit.

I cant imagine why folks stretch a truck. A new set of rails is 2600 USD installed on several models, both sides. the rails are 900 USD. JUST THE SAME, i VOTE FOR MEASURING CAREFULLY ON A LEVEL SHOP FLOOR TO BE Sure [sorry, caps lock]......

although bushings will cause some of these symptoms at times, I really think the best thing to do is go to Kenworth and have it put on the VisiCheck [aussie made, I think] and measure the chassis as the first 2 steps.

it is about $200 USD and will root out far more than a visual inspection and a torque wrench.

also, try backing into a curb stop at a store and see if your axles move. VisiCheck does this, and I seriously doubt this is your issue here, but I have done it, it is free and I have had success on my Air Glide 100 in the past. I did mine at pilot travel centre.

Hope this is of some benefit.

Tip: you can replace the rails with 12"Dx.375"W Grade 80 rails with a 3.5" flange / 1/2"radius. PG adams in burlington, vt is a good source. Ask for Ashley [?].

good luck

Edited September 24, 2011 by swjr

[Freightrain]

I took the truck out or a run the other weekend(truck club meeting), and the bounce is still there about 55-60 mph. No change even with the new rear bushings in the cross beam.

I was in the garage this evening and got to poking around and I think I found the root cause. The front bushings in the arms are bad enough I think it is allowing the beam to "bang" up/down on the front mount and this is the bounce I feel in the chassis. It is not as bad with the trailer(with the weight holding everything down).

The weather is getting better, so I'm going to get the truck outside so I have room to tear into it. I need to call Cross Truck and see if they have these bushings in stock also. Might have to wait to after Easter weekend as there is too much going on.

Time will tell, but I think this is the problem(I hope).

[smokin joe]

Have the steering axle checked king pins and bushings. My truck did the exact same thing. had to have some front end work done.

[Freightrain]

Put new tie rods on last fall. King pins should still be good. Did them years ago and don't get alot of miles.

I feel the bounce and see it in the rear mirrors. It literally shakes the whole truck.

[Rob]

I have a very aggressive bounce in my 80 R612 just above 45mph to about 52mph. It then goes away. This truck sat in one spot for a long time in the Texas heat so I'm thinking it may just need driven to smooth it back out. The tires are radial 24.5" and above 60%.

Rob