Truck Bounce

if it does it out of gear coasting down the road then you should eliminate the drive train .....if youre confident its in the front have you locked the power divider in and tried make any difference .............. check alignment most trucks need one anyway after time

 

I would love to see this truck! I am really curious as to the cause. I have seen diffs cause certain vibrations, but usually something ends up letting go or it gets worse over time. Wow, this is a neat problem. I can't remember without reading back, but have you checked your ride height? Possibly it is too low or high causing all the drive angles to be out which will cause weird vibrations.

 

well i'm going to throw something out here since its not fixed yet. I would say check the weights on the brake drums. if it threw one of them off it would be out of balance and unless you balanced the tire on the axle will never find it. I love spin balance rs the old style on the vehicle but no one uses them any more and hardley any one balances the dual wheels either or if they do they ballance them as singles which stiil want ballance the assymbly. I allways ran the cintrifical balancers on mine and got alot better tire wear.

 

Did you ever get it figured out?

 

I have 2000 Pete 379 that we've had since new and in the last 8 months or so its developed a similar bounce. It's way worse when it's loaded heavy (over 120,000LB) We've checked the shocks,tires, steering box,engine/trans mounts,carrier bearing and u-joints and are going nowhere fast. I put it on the chassis dyno last week and the only thing we saw was a little bit of front to back movement on the front drive axle. This was at 45 mph or so. My safety is almost due so we are going to pull all the drive wheels off and check for bearing issues or maybe a cracked drum. We haven't seen anything in the fluids to make me think the rear ends are going out. The bushings look ok on the suspension (pete air track) but it will be going in for an alignment soon (put 8 new Michelins on it because it feels like a tire issue) Post back if you find out whats happening.

 

I have the same problem with a 2005 379, changed everything you can imagine, Eveywhere I have had it they all tell me the samething, run it til it breaks, cannot find the source..

 

my 94 kenworth had a bent frame from factory and it was a very common problem that kenworth wont admit or i should say hates to admit . Causes lots of wierd handleing.

 

my guess is out of round brake drum on steer"maybe"