M917

[Construction]

I have an M917 and am looking for advice on the air shift front axle/diff lock.

Has anyone had any issue with it not engaging?

 

[Danger Ranger]

EDIT: Just realized Im an idiot. M917 is real, just not as common....doh!

 

[NDT]

What are the symptoms? I will assume no pull from the front axle when engaged: Check for air pressure to the diaphragm and no ruptured diaphragm. Check that the front driveshaft does not turn by hand (if it does, something is broken in the axle). If all this checks out good, the transfer has internal issues (Yikes).

 

[wreckerman893]

I'm doing this from memory so bear with me. The M916 I drove did not have a switch to engage the front axle....it was engaged when you engaged the power divider to lock the rear axles. Have you tried engaging the power divider and see if the front wheels pull? Or is that the issue?

 

[Construction]

The rear axles lock up fine, the front is just not pulling. I do not hear the "thunk" like I hear in my M920 when I flip the switch in the cab.

Anyone ever taken the diaphragm apart?

 

[goodguyzy]

I’m having a problem on my 916, both rear and front won’tengage but haven’t tackled the problem yet.

 

[Construction]

My issue is from the switch to the diaphragm on the transfer case. It worked off and on for awhile, but now not at all. The switch/valve body on the dash feeds air to the diaphragm which engages the front axle. When it works you hear and feel a "thunk".

There is also an air relief valve or similar connected between the switch and the diaphragm. It is behind the dash. I have not been able to get to it yet. I know because I hear it release air when it engages and disengages in my 920.