M936 Wrecker- Goes to Full Throttle When Crane is Engaged?

[WildernessJeep]

So I've used the crane a bit, and it's fantastic! The first few times I used the crane I was working on the throttle linkage (disconnected), so I shifted it at an idle in neutral and manually turned up the throttle to about 1500 rpm's on the fuel pump. I've now reconnected the throttle linkage and when I engage the crane lever (behind the seat) it sticks really bad, and when it finally engages the engine revs up to the governor and stays there. I watched the Youtube video about the crane operation, and he used the dash throttle to set the RPM's (it wasn't automatic). I'm not entirely sure I reconnected the throttle linkage correctly. I'd rather not run it at governor the entire time I run the crane because it seems like unnecessary wear on this old truck, it's really loud, and it makes the crane act like a psycho with super-sensitive controls. What am I doing wrong?

 

[fasttruck]

At least the M816 had a throttle under the boom near the power divider to set the RPM using an auxiliary devise on the fuel pump to control the rpm. Using the dashboard throttle was an issue as the NHC250 Cummins would gradually ramp itself up to full throttle regardless of where the dashboard control was set. Throttle is middle lever in pic 1. Pic 2 illustrates the fuel pump used on a wrecker. Both pics are of a M816. I understand M936s with the NH250 would be similar.

 

[fasttruck]

Make that the throttle control is the furthest lever from the camera next to the winch. Other levers select winch or crane and which way the winch would run. "Trolley" handle is an air control to operate the vehicle clutch from the back of the truck.

 

[doghead]

When using our forums please update your threads and not start a new one for everything. Several of your new threads should have just continued since they all pertain to the same issues.

Please take time to download the manuals for your truck and learn how to properly operate your truck.

 

[WildernessJeep]

I don't have any winch controls like that at all. My rear winch controls are on the passenger side of the bed, operable from the ground. I haven't seen any throttle control on the bed or crane at all, but I'll look. I do agree the dash throttle is tough to "set once" and it does creep, so it makes sense to have a seperate control in the rear somewhere. That control may be stuck wide open and it is causing the issue.

 

[kubotaman]

That's normal. Was part of an MWO on M936/A1s. M936A2s didn't get it, but my M936 did it as well. Definitely catches you off guard at first.

MWO-9-2320-272-20-4 - Page 1 of 20

NSN Depot - Advanced NSN Database with NSN Search

www.nsncenter.com

Automatic Throttle Kit 12357085 2910-01-290-0738 M936 M936A1

Surplus du Saintois - Automatic Throttle Kit 12357085 2910-01-290-0738 M936 M936A1 Wrecker US Army Truck MWO 9-2320-272-20-4

surplus.saintois.com

 

[simp5782]

936s need to run at 1600rpms or more while running the wrecker unit or you will burn the transmission up.

M39 and M809 series trucks can run at idle

 

[charlesmann]

the higher your rpm is, the more sensitive and faster the hyd will be. opposite for low rpm hyd use, the controls will be slow and sluggish.
i do wish i had an auto throttle, but I'm fine with setting it before i get out of the cab, for now. if i notice it starting to creep, ill figure something else out.

on the back right tread way area, right of the rear winch. is that your long boom supports?

 

[fasttruck]

Reference post 8: yes. Truck did not have the actual poles but I think they were supposed to be stowed next to the spades on top of the boom.

 

[charlesmann]

Reference post 8: yes. Truck did not have the actual poles but I think they were supposed to be stowed next to the spades on top of the boom.

my donor 936A2 had the set, stowed on the left (driver side) bed, closest to the bed rail. i wasn't sure his was the support poles or a tow bar.
not sure why the poles would be stowed on top of the boom. them things are a bigger to move around by oneself. I'm not getting rid of mine yet. but if i don't use them in the next few yrs, ill definitely be getting rind of them, along with the wiffle tree.

 

[fasttruck]

Mine had a bracket on the side of the bed for a tow bar. Sold truck 3 years ago so I can't walk outside and check anymore.

 

[fasttruck]

Reference post n11: if someone checks the operator's manual I recall there are detailed instructions in there as to the recommended stowage for all the OVM.

 

[charlesmann]

Reference post n11: if someone checks the operator's manual I recall there are detailed instructions in there as to the recommended stowage for all the OVM.

there is. i was looking them up for the dif between the 2 models

 

[WildernessJeep]

the higher your rpm is, the more sensitive and faster the hyd will be. opposite for low rpm hyd use, the controls will be slow and sluggish.
i do wish i had an auto throttle, but I'm fine with setting it before i get out of the cab, for now. if i notice it starting to creep, ill figure something else out.

on the back right tread way area, right of the rear winch. is that your long boom supports?

Yes, the long boom supports came with the truck, but they are on the wrong side of the truck. I haven't been able to get the crane working well enough to move them to the other side. They are at least a 4 man lift each (for old guys).

 

[charlesmann]

You aint kidding there. I used my tractor to move them from my field off the old truck, to the house and dumped them in the bed. Then had man handle them into place. Eventually i’ll stop long enough to figure a way to move them w/o equipment, by myself. But age is catching up fast, at 41, i need to figure easier ways to move heavy things, ie. my sawmill that im building. Motor alone weighs 700 lbs. and drive axle housing for it is an easy 80 lbs.

 

[M936A1]

My M 936A1 had the auto throttle lever turned backward when I got it. ( round carriage bolt face to the front of engine away from air cylinder rod . )
The auto throttle did not work it went to 2100 rpm when i put it in pto mode. (Shifted in to pto and pulled lock throttle)
I don't think the wrecker was used much and the lever was turned over to not cause problems for street operation.
Took quite a lot of staring at it to discover someone had turned the lever around . ( May have rolled out of the factory like that.?

Took me a bit to figure out how it all worked. ( head scratching ) (more head scratching )

Non pto mode
The variable speed governor is pegged at high idle with a spring in non PTO mode and when you pull the lock throttle on the road governor, the engine goes to 2100rpm (high idle) allows limiting speed gov to controle engine speed .( ie fuel peddle )

Pto mode
The air cylinder pushes the lever back to the 1500 rpm setting on the variable speed governor when the switch on the pto lever trips the electric air valve.
when using the rear winch or crane functions light on dash should light.

 

[gstirling]

So I've used the crane a bit, and it's fantastic! The first few times I used the crane I was working on the throttle linkage (disconnected), so I shifted it at an idle in neutral and manually turned up the throttle to about 1500 rpm's on the fuel pump. I've now reconnected the throttle linkage and when I engage the crane lever (behind the seat) it sticks really bad, and when it finally engages the engine revs up to the governor and stays there. I watched the Youtube video about the crane operation, and he used the dash throttle to set the RPM's (it wasn't automatic). I'm not entirely sure I reconnected the throttle linkage correctly. I'd rather not run it at governor the entire time I run the crane because it seems like unnecessary wear on this old truck, it's really loud, and it makes the crane act like a psycho with super-sensitive controls. What am I doing wrong?

View attachment 794477

i have an m936A1 with auto throttle, and my truck when you engage the crane (handle by the seat next to the door) - the auto throttle will take the truck to 2000rpm or so and then quickly back down to ~1500rpm, and when disengages does the reverse - engine roars to 2000 rpm and then dies down to true idle at about 700 rpm.