M939 Recovery / Extraction Shaft

[Swamp Donkey]

One of the mechanics at work used to be a mechanic in the military years back. I drove my M923 to work the other day and he told me that he wanted to tell me some things about it I probably didn't know. Most of it I had already figured out but he mentioned something that intrigued me. I was even more interested when I haven't seen anything mentioned here and couldn't come up with anything in a search. I'm not sure what it might be called so the search might have been pointless.

Basically he said that when they had a M939 series stuck, they had a long driveshaft that could be bolted to the axle flange of the stuck truck and the axle flange of the recovery truck: back to back, front to back, or front to front. This would give extra traction and power while synchronizing the operators during recovery efforts. Basically you would have 12 powered wheels instead of 6. You could use multiple shafts to connect multiple trucks in extreme cases. The stuck truck could also be incapacitated and the system would still work, although the recovery trucks engine would be doing all the work.

I have no reason to doubt him, and it seems feasible, but I have never seen something like this mentioned here or anywhere for that matter. He also mentioned he had seen it used twice and it worked where a winch didn't. Has anyone seen or heard of these? Was it military issue or homemade?

 

[doghead]

It may have been unit level hallucinogenicly fabricated

 

[Suprman]

I don't think applying drive power to the rear axles thru the transfer case would be good for it.

 

[wreckerman893]

I been to five marrins, three burins, two rodeos and a goat ropin an I ain't never seen nothin like that.

I recovered vehicles using just about ever authorized (and unauthorized) method and never even heard of doing a recovery like this.

The trucks would have to be joined together some way to keep the axle shaft from coming loose if you were using a whole driveshaft with the splined section in it.

If the trucks were hooked back to back or front to front wouldn't the wheels be turning in opposite directions?

My olfactory senses detect a rodent.

 

[patracy]

I have a fine bridge for sale as well.

 

[dawico]

I am just trying to imagine the nightmare that is getting the length and index perfect to hook it up.

Why would you even need to do that unless the stuck vehicle didn't run?

It sounds a little far fetched to me.

 

[Swamp Donkey]

Past hallucigenic experiences could be a factor, but he doesn't seem to be the type and he's not much of a joker either. He's been correct on everything I've inquired of him so far without even walking over to the truck. I figured he may have gotten some different things mixed up.

I had two concerns which led me to post about it. The first was that a bracket for one of the air valves and part of the bumper hang in front of the front axle flange, so there is no way to connect a straight shaft. The other was the problem of getting it bolted to the stuck vehicle if the flange was buried in the mud and water. It doesn't seem like an easy task even if the top part of the axle was not buried.

I'll ask him some specifics tomorrow and see what he says.

 

[Suprman]

Maybe it was some type of towbar he was describing connecting bumper to bumper for a solid connection between trucks.

 

[Artisan]

If I had a towbar that I fab'd up that was, Lunette Ring X Lunette Ring,
and if I connected said towbar to the rear of my truck at the pintle hitch
and then to the rear of a mired truck we are pretty much solid. Right? Right...
So were butt to butt, (please, lets be professional here you fags... )

Now, if I add a propeller shaft from the rear open spinning flange on
my rear-most axle on my 5 ton to the same flange on the stuck truck,
and if I hit the gas in my truck, it will spin the stuck trucks axles so that
all will go the way I want to go right?

I think this could work...can anyone, a diff pro prove "us" wrong. And if
the front axle is engaged on the stuck truck it would turn it too yes? So
you would have a 12 wheel drive (if singles) but independently powered!

This might work! Sound like something I would do! Ha!

 

[Artisan]

PS, where can a guy buy a cheap flange that will connect
to that rear, open spining flange?

 

[Suprman]

If you were back to back with the 2 rear diffs linked the truck you were pulling out would be driving away from you.

 

[Castle Bravo]

The axles don't care about the facing direction of the truck - If you have it hooked back to back, it would work. The axles turn one direction clockwise and the opposite counterclockwise. The "towed" vehicle's axles would turn the same way as the "towing" vehicle no matter what the orientation.

 

[Artisan]

The axles don't care about the facing direction of the truck - If you have it hooked back to back, it would work. The axles turn one direction clockwise and the opposite counterclockwise. The "towed" vehicle's axles would turn the same way as the "towing" vehicle no matter what the orientation.

I am inclined to agree cb, I do believe this would work.
I can draw in CAD that flange but it sure would be nice
to have one in hand to measure instead of off the truck
so I seek one of those flanges if anyone has one. Send
it free and if/when I get a mate I will give you one free.

LOOK IN POST#9, I WANT THE FLANGE I AM POINTING AT!

 

[wreckerman893]

The truth is stranger than fiction judgy wudgy.

Okay......now my interest is piqued. I have the driveshafts that came out of the M927 I scrapped out.

My first suspect would be the one that ran from the front axle to the transfer case because it is long and has the splined shaft section.

I have my M927 and the loaner M927 that is holding down a section of the back 40.

I have a welder and lots of junk to fab some brackets to hold the trucks in a fixed position using the shackle mounts.

I have too much time on my hands.

If my attention span can handle it I may see if the shaft will actually connect up without a lot of hassle.

Don't change that dial.

 

[Csm Davis]

Wrecker just use a tow bar and the drive shaft. I have heard guys tell me this before and I say it might can be done rear to rear but the front has things in the way. Also this would be a useless hookup unless the stuck truck was dead.

 

[Artisan]

snip

but the front has things in the way. snip

There is no round companion flange open and spinning in the front, I do believe, FWIW.

 

[rhurey]

Uhh????



View from the bumper looking aft. Pretty sure it spins...

 

[Castle Bravo]

There is no round companion flange open and spinning in the front, I do believe, FWIW.

 

[JMPM35A2]

Im now interested.

 

[Swamp Donkey]

Some more about information I dug out of him today...

He was present at the site of the stuck truck but was about 50 yards away working on another truck with a broken U-joint. Apparently there was no wrecker available so they tried the winch truck. Then they tried snatching with another truck which broke the U-joint. He was not present for any of this. By this time he had showed up and the shaft had been installed between a 3rd truck and the stuck truck. He didn't get to see installation or removal but was adament that it was hooked back to front, which is where I don't see this working unless parts were removed. The shaft appeared solid and would had to have a U-joint in each end but he was at a distance so couldn't confirm. There were no other connections except the shaft but it was larger in diameter than a standard drive shaft. It was then driven out like it wasn't even stuck. He said there was very little wheel spin at all.

The second time he saw one it was being used by the same unit. They were just passing by though, although a little closer this time. I asked if maybe it was homemade since apparently he has only seen one and he said it could've been but was not sure.

I can see this connection working easily back to back. If both trucks were running, one would be in forward and one in reverse and you would effectively have 2 engines powering the now singular, combined drive line. I question whether those flanges would be able to handle the stress without a solid connection between the 2 trucks. This would seem to be a substantial amount of stress when one vehicle has more traction than the other, which would be the case in the situations they were being used in. The flanges would endure both rotating and pulling forces until the traction was equalized between the two trucks.