Lighter springs on a 939?

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Buffalobwana

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Anyone try it up front? The front suspension on these trucks is too much for what *most* of us use them for. The 2.5 or 5 ton ton LMTV springs seem a bit small, but I see there are MRAP springs available too.

Im just looking for an alternative to the giant steel timbers on the front that are currently compressing my spine. Rear springs need help as well, while
maintaining ride height.

When I drove down to help with the Harvey rescue, I had the bed full of bottled water. Was the nicest ride I have ever had in that truck. (It was a lot of water!)

Even with 5 tons of feed in the bed, its still a bit rough. There has to be a reasonable middle ground somewhere.

Im working on turning one of my trucks into an expedition vehicle
with the S-280 on the back. I can tolerate the ride with the air ride seats, but this project will go a lot smoother if my wife doesn’t hate the way the truck rides.
 

snowtrac nome

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what makes the lmtv springs work is the length. the 5 ton springs are stacked up short and tight removing a few of the shorter springs in the pack would improve your ride, but to maintain ride hight you would have to add spacers or lengthon the hangers.
 

Buffalobwana

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what makes the lmtv springs work is the length. the 5 ton springs are stacked up short and tight removing a few of the shorter springs in the pack would improve your ride, but to maintain ride hight you would have to add spacers or lengthon the hangers.
Yeah, I had wondered about that. I thought removing every other one, maybe 3 total, then cutting them down to fit toward the bottom of the stack, to serve as spacers might work.

Like to see if anyone else else has tried it before I have them cut.
 

Buffalobwana

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While we are talking about it, has anyone tried putting air bags/shocks on the back of the cab in place of the cab mounts? Basically, mimicking the air ride cabs in big rigs.

I realize all this may sound a bit excessive for a typical 5-ton, and it is, to a certain extent. But, I’m building this into an expedition vehicle, and long days on the road, and off road, need to be more comfortable than a truck I would only drive 100-200 miles a month.
 

simp5782

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Not enough room for the cab air bag unless you refab a crossmember. Air bags in the front is possible. Parabolic springs are also a good choice for the front
 

snowtrac nome

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if you want flex get rid of the short springs leave the longer ones in, generally spacers in the front aren't recommended I have seen some commercial rigs set up that way from the factory.
 

Buffalobwana

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if you want flex get rid of the short springs leave the longer ones in, generally spacers in the front aren't recommended I have seen some commercial rigs set up that way from the factory.
The only reason I’d use chopped down springs as spacers, is to maintain ride height. Heat isn’t a springs best friend, but if it’s a shorty, used as a spacer, with no flex, Im guessing it would be fine.
 

cucvmule

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I do not know which tire size you currently have on the 939 but is it possible to use a tire with a softer sidewall? Just wondering, if you do not plan on transporting heavy weights then maybe a little help in using the tires as a cushion may help.
 

Lukes_deuce

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Just a thought, if your setting up the truck for overlanding, are you dead set on keeping the truck 3 axles? I had a buddy bob his truck and add a peterbilt rear air ride. That truck floated down the highway. Very nice ride and he was on 16R20s as well. It had a single leaf spring for controlling axle position and the air bags carried the weight. It flexed very well off road and I think it was rated at 21k or 22k load? The suspension was for a single rear axle box truck.
 

Buffalobwana

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Just a thought, if your setting up the truck for overlanding, are you dead set on keeping the truck 3 axles? I had a buddy bob his truck and add a peterbilt rear air ride. That truck floated down the highway. Very nice ride and he was on 16R20s as well. It had a single leaf spring for controlling axle position and the air bags carried the weight. It flexed very well off road and I think it was rated at 21k or 22k load? The suspension was for a single rear axle box truck.
Yes, I have. You are right, that would solve a big chunk of the ride issue. And it’s a great idea, unless traction is paramount.

I guess you should never say never to anything, but I’m opposed bc you are removing the benefits of another axle pushing an already heavy truck through sand or mud. You air down tires to gain traction which increases your footprint by how much? 15%? 20%? Three axles is 50% more grip than 2 axles. That’s substantial. The truck is heavier than most of its 4 wheeled adventure vehicle counterparts like the Mog or LMTVs. When they get up to this weight, most have 6 axles.

I have thought about designs for airbags on the rear. It would limit articulation when aired up, but allow a fair amount of articulation when aired down.

I saw Wes had a video about installing bags on the rear of a 939, so now I can’t take complete credit for the idea, although, my design varies from his.
 

Csm Davis

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The military actually made air ride rear 939's and profo has air bags up front. I am going all air ride with my XLWB 932A2. I am doing front, rear, cab, seats, and trailer already has rear air ride, and air ride king pin.

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Buffalobwana

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The military actually made air ride rear 939's and profo has air bags up front. I am going all air ride with my XLWB 932A2. I am doing front, rear, cab, seats, and trailer already has rear air ride, and air ride king pin.
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That sounds like something I need to see.

Can the cab be put on bags in the back (with necessary modifications) using the front mounts to pivot off of? Do you have to raise the front of the cab a bit? I assume they have little shocks to dampen the bounce? Where do you get “kits” to air ride the cab? Or do you just piece it together?
 

Csm Davis

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That sounds like something I need to see.

Can the cab be put on bags in the back (with necessary modifications) using the front mounts to pivot off of? Do you have to raise the front of the cab a bit? I assume they have little shocks to dampen the bounce? Where do you get “kits” to air ride the cab? Or do you just piece it together?
I have looked at lots of over the road trucks and I believe that we can just graft the cab rear mounts and bags and shocks on to the rear of our cabs, but I don't know if the hood to cowl mating flange is going to need attention. I originally was going to be 4 dooring my tractor and it would have much less movement at the front than our day cabs will.

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