M817 5 ton Dump, front axle Questions

[Dirtydeedsmx]

Truck front diff engages fine in reverse but not in forward gears. While in reverse air is bleeding out of pop it valves constantly, air seals off in forward. Any suggestions?

 

[eric67camino]

Truck front diff engages fine in reverse but not in forward gears. While in reverse air is bleeding out of pop it valves constantly, air seals off in forward. Any suggestions?

Engaging in one direction and not the other sounds like the one way sprag clutch could be damaged.

I would check your air lines going to the transfer case for leaks. I had one split there before.

 

[Dirtydeedsmx]

Thanks. Is there supposed to be constant air bleed off on pop pit valves in reverse ?

 

[NDT]

Thanks. Is there supposed to be constant air bleed off on pop pit valves in reverse ?

Nope

 

[Tow4]

The transfer case air cylinder is also prone to leaking. If the leak is bad, the transfer case won't engage the front drive. It's easy to rebuild if that's your problem.

Transfer case air cylinder rebuild.

 

[tobyS]

How are you checking engagement? The front turns at a different rpm than the rear and the sprag does not lock in unless the rear is slipping. The front is like 16/1 and the rear is 17/1. Sprag releases the difference. You should hear the cylinder shifting forward to reverse but no air leaks.

The only way I see to check is to jack all axles up and run it slow.

 

[Dirtydeedsmx]

I’m hauling dirt in sand,, while running in forward the rear will start slipping with no evidence of front engagements. In reverse you can see the front pull when rear slips. Thanks for the input! Didn’t know about the difference in ratios.