jumping brakes

Make sure that there is enough air in the front axle and not to much in back. It may have two leveling valves so check on that. Also see if the service side of the brake chambers is all ran off the same valve and not two different valves. If it has two different service control valves one of them my be malfunctioning. Or maybe one has different crack pressure.

 

Did the problem start after you had the brake job done? Does it do this when empty and loaded or just empty?

 

Did they replace the s-cams and bushings when they did the brake job?

 

You might just have to put an air pressure gauge at the line going into the maxi for each axle to make sure the application air pressure is the same. If it is, then you are looking at a mechanical problem and not a pneumatic one. Either there is some thing wrong with brakes, like a shoe to drum miss match, bell mouthed drums. On air ride suspension, I have seen one axle get air bag pressure, but not the second one, so it will skip and bounce when braking simply because it has no weight on it.

 

maybe the shocks need replacing