Another bobber thread!!

Now first let me State I have searched. And I’m not finding exactly what I’m searching for.

I know there are a few options out there, mrap, and 5 Ton fronts, full air. When I bobbed my deuce there was a plethora of after market parts out there, saddles, perches, blocks, hangers, etc. with the 5 ton I’m coming up blank on most of this besides oem.

The problem arises because of the direction I want to go with the truck. I’m basically looking to build a 5 ton dump. I found what I believe is a good deal on an m931a2. But, I can’t imagine 5 ton springs are up to the task by themselves.

This is brings me to my few options. And I’m looking for input as I want this to be a safe 5 ton dump, hence right now the spring options are my limiting factor.

Here are the options I have come up with, any input is greatly appreciated.

Buy a factory 5 ton fronts and have my local spring shop ad leafs, they admitted then can do this but can’t tell me exact rates or specifics, just they they can add leafs, or remove leaves and ad thicker ones. Not a terrible plan but not as precise as I would like to be.

Take me my local spring shop the exact measurements of a 5 ton spring, and see if they can come up with a spring close to the same measurements with my desired rating, since I’m bobbing length isn’t an issue.

Or mrap front springs. I have seen them in a lot as advertised as 20k but have no idea if this is accurate, nor have I seen much feedback how they would do with 10k on them plus the weight of the truck, I.e flex and ride quality loaded.

Im trying to figure out this hurdle before I pull the trigger on this truck, if I can come up with a good solid option then Ill probably pick the truck up.

931xx is not that long, so whatever bed you are putting onto it will not be able to hold all that much weight.

I'm not a spring expert, or expert at anything really, but it makes me nervous when people start adding leafs to an existing spring, because the top leaf remains unchanged, and this is really the one that is supporting the rest, and the only one secured to the truck (so if this leaf breaks, you know what happens). If you plan to load it down with more weight than the front of an M939 spring pack is designed to handle, then I'd just go to a heavy duty spring shop, and get spring packs for the weight you intend to carry. They are not that expensive.

I don't think this is solvable until you know the box weight you want to put on, in addition to the load capacity limit you want to set (and separately, plate for).

From what looking I have done I’m looking at a 9 or 10 foot bed with 3-4 foot sides. That’s what seems to be on most 5 tons. I don’t really like adding springs either but I’m almost positive they could add a new top thicker leaf. I need to stop and see what my options are but the guy wants the measurements of the front springs.

I'm not one to stifle innovation but you seem to be going in two directions. If you have a good M931A2 in your sights and want to turn it into a dump truck, no confusion there. Wanting to bob it into a single rear axle truck is where I'm confused. You could keep both rear axles as built and the truck would handle the weight of the dump bed with no changes needed as far as suspension goes. For what it is worth, the M929A2 is built just like the M931A2 with the exception that instead of a 5th wheel plate it has a dump truck bed and the necessary components to make the bed tip. The tractors and the dumps have the same length frame "short", standard cargo's have "regular", extended length cargo's, expansible vans and wrecker's have "long" wheelbase frames.

Inline6359 said:

From what looking I have done I’m looking at a 9 or 10 foot bed with 3-4 foot sides. That’s what seems to be on most 5 tons. I don’t really like adding springs either but I’m almost positive they could add a new top thicker leaf. I need to stop and see what my options are but the guy wants the measurements of the front springs.

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Where are you going to position the axle, and are you going to shorten the frame?

sandcobra164 said:

I'm not one to stifle innovation but you seem to be going in two directions. If you have a good M931A2 in your sights and want to turn it into a dump truck, no confusion there. Wanting to bob it into a single rear axle truck is where I'm confused. You could keep both rear axles as built and the truck would handle the weight of the dump bed with no changes needed as far as suspension goes. For what it is worth, the M929A2 is built just like the M931A2 with the exception that instead of a 5th wheel plate it has a dump truck bed and the necessary components to make the bed tip. The tractors and the dumps have the same length frame "short", standard cargo's have "regular", extended length cargo's, expansible vans and wrecker's have "long" wheelbase frames.

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Several reasons actually.

Scratch the bobed 5 ton itch, and dump in one swipe, a tandem is overkill for the bed size. The truck will mostly be used to move horse **** to the landscape place that takes it, and stone here and there from my local supply yard to my house 500 feet down the road. Third, the truck will need tires anyway, and 1600r20’s would be used so I don’t need the extra axle nor tires to handle the weight. It’s mostly to scratch the 5 ton bobber itch.

Jbulach said:

Where are you going to position the axle, and are you going to shorten the frame?

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all depends on the bed I get, and the springs I come up with. So that’s up in the air, if possible I would like to keep the place for a spare and still be able to place the dump with no frame modification.

I had an 817 and currently have an M929A2. Having recently hauled 15 loads into a muddy lot, I doubt if a 4x4 would have made it in or out. Maybe with 16.00...but I doubt it. I hated the 14.00 GY AT2 and went with 395's...and glad I did. I'm working on my M35A3 6x6 to 4x4...also with no frame changes. No way would I consider shortening the frame (the true meaning of "bobbing").

I don't know where you get the idea that the short bed cannot have a heavy load...IT CAN, especially with high sideboards. Large stone and chunks of concrete add up fast.

A real limiting factor for all of the 5 tons is their problem reversing in low range.....I don't seem to be able to avoid it.

On the plus side...there are a lot of nice M931's out there. I would like to have the trailer air control as well.

FYI I have a new PTO if you want one... have a special for one (only) going FindlayO with GimpyRobb.

Why not make it an air-ride set up? Ive seen two bobbed M923s with air-ride and they ride great. Not sure on the weight rating but the set up is for a 6 wheel peterbilt. Should be the standard 23k rear axle.

I just made my m923 into a dump with the original bed. Not sure on what bed your going to use but make sure the hoist is strong enough. Loading up a short bed with 5-6 tons and no over hang on the rear will take a lot of hydraulic effort.

Maybe it’s just me, but over the years I have had way more luck with all wheel drive dumps then 2wd. This isn’t an end all be all for off road use, or something I think can magically not get stuck. It is simply a better alternative then a factory dump to lessen the headache I get when I have to do something in crappy conditions. And after looking at all wheel drive internationals, I can build two 5 tons for what they are asking for an all wheel drive truck. And that’s the cheap end.

I never said a short bed cant be heavy, so I’m not sure where you got that from, I said for my purposes a tandem is overkill for my needs. This truck will haul manure 95 percent of the time and hay from our storage to the barn. Stone here and there. Any large loads I can have delivered. I need a truck that dumps and can make it to the barn in the winter or wet conditions. This winter it took me 3 hours to load the dump trailer I had because I had to track it 1/4 mile at a time to load the trailer and back, because I couldn’t get the dump to the barn. (It was a big dump, and steel tracks on ice didn’t help). And most times I don’t have the luxury of waiting for perfect conditions to do what needs done. So, I’m simply trying to build the best option I can.

If if I go with a. Conventional pto I’ll hit you up. I’m looking at hydraulic power units as well as serpentine driven pumps.

I had to put loads down into the hole (8') with soil leaving a 14" rut around it. I backed onto my piles and the articulation was incredible. There was no way it would have went where it did as a 4x4. For a work truck, my $02 is leave it 6x6....for a play truck, I like the 4x4.

An air locker....maybe (wonder if they make one for the deuce (my 4x4 project)).

I had the nicest M931A2 of the many trucks I've had that I thought about doing the same thing... but the cost of a complete end push dump new at $10k kept that from happening. Obviously I like the idea but after making plans for several dumps from cargo's and not doing it, bit the bullet for a 929.

It would be worth more, have higher functionality (traction, load capacity, etc....), and look better (my opinion) as a tandem. As a single axle rear, you will likely be taking away from these, at least 2 of them anyway. Each their own, but as many others here also, I'm not really down with a "bobbed" truck.

I guess the point blank answer is, it can do whatever it wants in 6x6 but I don’t want a 6x6 truck? I want a 4x4, 5 ton. I don’t need, nor desire 3 axles? A 5 ton with rated tires and springs will do just fine. If I needed a tandem this would be an m931a2 dump thread not and m931a2 bobber thread? So anybody with the input about the spring options please come forward.

Then why reply? I mean honestly? This isn’t an opinion thread, I’m like looking for real world results.

If you want it to be safe and correct as you say, then use correct load rated parts. Tires, springs, axle, etc. Beyond that, not sure what you are looking to have answered. I’m not even smart enough to know if a 5 ton is still rated for 5 ton if you shed one rear axle. I would guess no, but no idea.

I think the springs off the front would likely work fine, maybe add a few full length top springs under the two main leaves. If your concerned check with junkyards that deal with big trucks, you should be able to pick up 20k springs and front hangers fairly reasonable or at least compare to a 5 ton. Not sure if you have the truck yet, if not let me know if you want some specs and pics of the front springs.
You may also want to look at some stronger wheel options if you plan on running 20k or more...

Inline6359 said:

Then why reply? I mean honestly? This isn’t an opinion thread, I’m like looking for real world results.

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Good luck with that. We just sit dreaming...none of that real world stuff here.

Bobbed M35 with dumpconversion

I went to a local salvage yard and found a set of 22 ton springs for my M35 bobbed truck which was converted to a dump at the same time. I cut 32-33" off the rear of the rails, and installed the single spring set with grade 8 bolts. I also cut the bed down by sectioning it to keep the factory look but shorter. I sectioned the sides at the rear and the bed at the front and have loaded it with wet dirt and it has held up very nicely. I believe the hoist I used was rated at 10 tons and has worked well except for the 12 VDC pump it came with. I have since swapped out the hoist pump to a 24 VDC unit and it seems to lift a bit faster and the batteries hold up better too. Only complaint is speed at this point and I wish I had gone with a PTO powered pump from the start. One day.

Bobbed M35 with dump conversion pictures

I built a sub frame out of 2X2 square tubing and bolted it to the original bed mounts so the entire bed with lift can be removed if needed. The pump is also mounted to the sub frame as can be seen in the first two pictures.
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So Ive been thinking about this. Came across a very similar suspension that I know a guy put on his M931 to bob it.

https://freightlinerads.azureedge.net/AirLiner_SS_041812.pdf

Im pretty sure it was the older model to this. Truck rides great and has good articulation as well. The single axle suspension is rated for 23k pounds. Not sure what the front is rated for on our trucks but I remember 12k. So 12 + 23 = 35000 pounds. Take away 15000 for a bobbed truck and you end up with 20k payload. Seems like a good amount. Will probably be over loaded on any tires besides 1600s. How short will the bed be? Will you have the volume to load it up that much? Lets say an 11 foot bed, 7 foot wide by 2 feet high gives you 5.7 yards, rounding up to 6 yards then taking bulk material on the heavier side of 2500 lbs per yard and thats 15000 pounds. Go up to 3 foot sides @ 2500lbs per yard and your at 21400 pounds.

With my dump set up, I have the stock bed and would be happy with 6 to 7 yards in it. Time will tell if the hoist will dump it.

Here’s my .02 if it is a part time dump truck build a standard bob with the axle as close to the pivot pins on the dump bed as possible put in a air bag for extra support when needed put in a dump valve on the air bag plumbing so you can drop the air when dumping the load this will add stability when dumping the load (most dump truck roll overs happen when dumping) have fun with the build