I have recently purchased a couple of trucks with chalmers suspension and am in need of a little help. I am sure that someone has probably posted something on this before but cant find anything. the problems that i am having is one of the trucks seem as the rear of the truck is drifting from side to side while driving down the road. We have checked all of the bushings and they all appear to be tight. the main "big rubber bushing" that is in the middle of the walking beam seems to have the most flexibility. Any ideas on what would be causing this? the other truck is not near as bad. I have thought about swapping the big bushing between the two trucks and see if the problem is transferred from one truck to the other. the chassis is a 2007 peterbilt bridgemaster mixer with a double frame and it has the same problem whether the bridge axle is up or down. Any help would be greatly appreciated. thanks ahead of time.:Banghead
Are you sure the problem is the rear suspension? Have you considered having the alignment checked?
I have checked all of the suspension bushing and the only thing that has some flex is the big rubber spring, i have just about ruled out a suspension problem, took an excavator, chain hoists, etc. to move the truck and force the suspension in many ways and no movement in the joints. next will be tires and axle bearing.
How about a broken frame? What you are describing was related to me by another fellow. He struggled with it for a week or so. could not find anything causing the problem, finally he found the frame almost completely broken in two. right at the rear of the mounting angle, about an inch in from the back. The break had been concealed behind the angle. Finding it had been a real mystery. According to the fellow that replaced the rail, this is a not a unique event. Makes me look closer every evening when I get home and put the truck to bed.
I'm not real familiar with the Chalmers, but don't they have trac rods running from the rear ends to the frame to prevent side to side and front to back movement? The broken frame (or cross member) sure sounds worth looking for.
Have you followed alongside in a car to watch for movement?
Pineknot, I am glad you brought this up. I have a 2006 T-800 quad dump with the Chalmers high articulation suspension also. Mine has just reached the 260,000 mile mark and is starting to have the same symptoms as yours. I await more input as I have checked everything on mine as well. :Banghead
The big rubber piece in the center has no effect on the tracking, it's just there to support the weight of the truck. The upper and lower control arms locate the axles. The same rubber bushings(16 in all) are used top and bottom, they are easily changed by hand, all you need is a socket and end wrench for the bolts. Change them out, one arm at a time. The ride can be adjusted by varying the size of the "can" that fits over the center bushing, the bigger one allows more give and the smaller size allows less deflection from the weight. When you buy control arm bushings be sure to specify standard size, the oversize ones are a really snug fit and are a real pain to install.
easiest way to check for sideways play is to load the truck and do a hard turn both ways and see how much space you have between the front and rear drives to the frame. if the tires are about to touch the frame or touching the frame, its time to change the wishbone bushings. Luckily Chalmers suspensions are relatively easy the repair
Like the man said put about 5 ton in and turn hard both left and right Check the distance from the tire to the frame. If it's not just about equal, front to rear drive then the walking beam needs some bushing work. Also to relieve stress on those walking beams, if it doesn't already have the double links from the diff's to the frame, you need to do whatever you need to get those links in! Man do they save the walking beam bushings!