5 Ton tractor to dump conversion

Eaglhawk

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Has anyone put the dump components from a M51 Dump truck onto a M818 Tractor truck?
I have Jack Tomlin's old beat up M51 and wish to put the dump components on a new M818. It looks like the rear frame length is the same so It should be straightforward to remove the 5th wheel components and put the dump components on it. Both have winches and pto's that bolt to the transmission.
Jack's old M51
IMG_2314.jpg

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My old M818, my new M818 one looks the same
IMG_2315.jpg

Does anyone know what issues I will have with the conversion?
I probably have to swap pto's from forward only to forward/rear version.
Holes might need to be drilled in frame for dump bed pivot?
Maybe there is a thread here with this conversion?
Thanks everyone!
 

tobyS

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It should be pretty straight forward since they are the same frame length and drive the pump in the bed frame tank. The hinge point is on the frame of the dump bed, so that should not be a problem. Yes, the PTO will need both front and rear which you already have on the M51, including driveshaft.

My 817 was a good truck...love them. I wanted to go to the M931A2 but never came up with the dump bed while I had the tractor.

What is the matter with the M51A2 that it can't be repaired?
 

tommys2patrick

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Will likely have to do something about the ramps on the rear of the tractor frame. thats where you would have to place the pivots. so strength issues from the conversion may come into play. Have you considered drive line swap instead. I am sure you know that dump trucks have a hard life on lots of major components. I presume you need the functionality of a dump truck and the 818 chassis / drive line improvements over the 51.
 

tobyS

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The pivots (hinge) are part of the dump frame that mounts to the frame rails of the truck. Ramps do come off but the hinge and cylinders, tank and pump (and I think valve) are all part of the dump bed frame. No frame alterations are necessary.
 

tommys2patrick

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I would have thought you would still need to rebuild the angled ends of the truck frame where the ramps come off as the pivots are directly above that on the dump frame. Perhaps the 818 ramps are attached to the frame differently than my m275. not that a bit of frame welding would be too much work for someone doing a project like this.
 

tobyS

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I would have thought you would still need to rebuild the angled ends of the truck frame where the ramps come off as the pivots are directly above that on the dump frame. Perhaps the 818 ramps are attached to the frame differently than my m275. not that a bit of frame welding would be too much work for someone doing a project like this.
They are bolt on and just need removed. Google M818 and look at the images (just like my M931A2).

If one has the machinery to take the dump bed off it's frame, during the change over may be a good time to rebuild select items, check for cracks in the frame/tank, etc.
 

eric67camino

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One thing you may run into is that yoy may need to swap the front mounting flanges for the bed subframe over from the other one.
 

tobyS

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Picture of my front and rear dump frame mounts (I don't think they are different on earlier models). Note the thickness of the spacer between the frame and bed frame. You may need the height but I'm not sure.
 

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NDT

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Your M51 looks super clean to me. All driveline components except for the engine are the same between the two trucks, what are you gaining by doing all this work?
 

tobyS

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NDT, that's what I thought after seeing the photo's...the M51A2 is really nice looking and good repair candidate.
 

Eaglhawk

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Thanks everyone for the input. The idea of swapping the dump over is because the trucks drivetrain is pretty beat up. Jack overloaded it many times and the ram lifting system was replaced when he overloaded it once and sheared the dump off once. I know because I had to re-weld the bed attachments and re-fabricate part of the dump bed about 8 years ago. Also when I bought it from Bob (Tomlin trust) I was told it was running without problems. After buying it and loading it to ship it to my yard it was making loud grinding noises from the rear. When taking it off at my yard and inspecting closely I found that the upper dogbone had pulled itself off where it bolts to the frame and pushed the rear yoke into the rear frame member.bending and grinding on it good (rubber bushing failure). Since the rear springs sag so much this kept the rear axle from rotating back and taking out the rear driveline which would be much worse. Looking at the issues to make it a reliable driver the thought of swap seemed worthwhile since I have 4 of these new tractor trucks just sitting with no miles on them and more horsepower.
Thanks again everyone for your comments!
 

Eaglhawk

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I really really don't like the dogbones on the 2 1/2 tons and the 5 tons. If the rubber fails and the dogbone pulls free it can cause catastrophic failure with the separated driveline swinging around and taking out the brake lines. This has happened twice to me and once caused me a wreak when towing a 2 1/2 ton with my 5 ton wrecker when the rear dogbone failed and took out my brake lines and rolled backwards out of control on a icy jack-knifing the duce into the side of the wrecker. I am looking at having a steel plate bolted or welded to the dogbone to keep this from happening.
 

tobyS

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Thanks for the explanation. From just the photo, the M51A2 WW looks like a desirable truck. It having a hard life and some repair/modification makes sense now.

I would surely bring the parts added to the 818 up to reconditioned standards, probably taking it all apart.

I do like the combination with the 250 and 5 speed, winch and 809 body style. Enjoy the build!

Dogbones....can be a pain and expensive. Do any of your tractors have them in good condition? Do you have a specific one picked out?

I was going to cut some very long rubber strips from tractor tubes to carry with me to hold the DB to the bracket and not pull off the end. I inspect them regularly and the first sign of rubber failure, I planned to make a bandaid fix, wrapping about 4" x 8' of rubber tight. Using tractor tube, I could get a long length around the perimeter. Just an idea, I am not doing the off road a lot, but when I have the chance, will add to my toolbox.
 
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Robo McDuff

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I started with an M51A2 and made it into an swapable M51 to M52 and back. I have the full description somewhere, but am on the road now without time to look for the papers. It should work out without too much problems.
 
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