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M936A1 crane ops- basic questions for engaging transfer case PTO

LCA078

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I'm going to inspect the crane hydraulics of a M936A1 that is reported to not work and I want to get knowledgeable on crane ops before I go see it . All I know is "PTO engaged but no hydraulic pressure to crane" so I'm guess this has a high probability of operator error. And yes, I have all the TMs. Even posting the crane ops section from the -10 here as I'm sure in the someone in the future will google this post who just bought a wrecker but never looked at the TM will wonder they can't get the crane to work. But I digress....

Here are my questions:

-After reading through SS and the TMs, I still can't get a good understanding of how the engine and transmission is supposed to operate together when the crane transfer case PTO is engaged. Per TM, the order of steps are: 1) shift t-case to neutral, 2) shift tranny to 1-5, and 3) set engine rpm to have hydraulic power. I see a lot of posts about the tranny up shifting gears when in 1-5 but I can't determine from the TMs if the transmission is supposed to up shift once the rpm is set. I've even seen folks say to use other ranges like 1-4 or go straight to 1-1. Does the tranny stay in first gear or actually up shift? How does this effect the PTO speed? I guess I'm really trying to understand how the tranny and transfer case PTO interact to power the crane pump.

-How can I tell if a truck has the auto-throttle MWO (but not functioning)? What would the device look like and where would it be located?

-I'll inspect all linkages for bent rods, etc. but I know there are a lot of interlocks and other things to worry about too. Is there is a particular one I should look at if I have trouble getting the transfer case PTO to engage? Any tricks not explained the TM that help since the -10 is really thin on troubleshooting? The one trick I've seen is to bleed down the air pressure to work around a bad t-case interlock air solenoid or cylinder. Anything else?

That's a lot of questions for now before I even see the truck so appreciate the education. Will keep y'all posted of what I find.
 

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Firemanmike69

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1)Shift t case to neutral
2)engage transfer case PTO, it's the one to the left of the driver's seat, not the one by the dash for the front winch
3) place transmission shifter in range 1-5
4)hand throttle to 1200-1300 rpm

The crane and rear winch run off the transfer case pto and the front winch has its own, maybe they were engaging the one for the front winch and assuming it operated everything?
I have been meaning to make a video about the operation of the wrecker and winches because YouTube seems pretty short on Information about it
 

KN6KXR

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I have an M936A2. I do the following:
1) Parking brake set, engine in neutral, at idle
2) Depress lockout solenoid at end of t-case shaft, wait to feel/hear solenoid engage, shift t-case to neutral
3) Engage power divider lever located to left rear of drivers seat sometimes I have to bump the transmission in and out of drive to get it to seat fully
4) Shift transmission to drive top gear
5) Use hand throttle to shift RPM's up to about 1700 I look/feel for the thump/bump as it hits 5th making sure it's in top gear
6) As I exit the truck I listen for the air brake dump (the power divider lever dumps the supply it's a secondary safety) and look at the PTO shaft it should be moving quite quickly
7) Operationally on the crane I should look at the hydraulic filter indicator and make sure it's not pegged over
8) As I move the crane with a load I keep an eye on the gauge I added at the valve block I have the relief set at 1350psi I should not be riding the relief

All I can think of at the moment besides the other basic checks (tank fluid level) and operation (shipping boom stays and such). These trucks have surprisingly little deck space make sure you clear the deck I carry some cribbing and more than once I've smashed it because I was in a rush. Also get your rigging out of the storage boxes first or open the lids the crane blocks you from opening the lids once you rotate it that way.
 

LCA078

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Thanks guys- appreciate it. I'll let you know what I find out. Wreckers are a new one for me so it will be a bit of learning curve when I get on it.
 
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