m939 A2.. if you could do everything possible ...

[sawdustnsteel]

keeping the stock 8.3l Cummins and the potentially the allison 5 speed.

what would you want to improve for the best possible performance ?

radiator?

turbo?

Wheels?

suspension?

Ideally id like to find out what gets a 5 ton 8.3l to ride easy on highways doing 80mph and 10MPG or better, is capable of fording 3 ft of water easily enough, won't leave you screwed in the middle of off road riding. et al..

make it a daily driver that doesn't get passed by school busses and Prius cars on the highway.

( an effort to compile all the inventive things Ive been reading on modding and rodding this vehicle. instead of having 40 threads to fish through, joining all the latest and greatest ideas in one thread.)

 

[71DeuceAK]

Great idea! I'm also curious. 80MPH and still a good off road 6X6, I would never even dream of bobbing or shortening mine once I get one.

 

[sawdustnsteel]

Great idea! I'm also curious. 80MPH and still a good off road 6X6, I would never even dream of bobbing or shortening mine once I get one.

I can't help myself IM tired of building Bikes so bobbing a 5 ton and building it out like a hulk version of a HUMMV is my goto Idea now

 

[71DeuceAK]

How about still a 6X6 but 80MPH and fast acceleration?

 

[mcmullag]

I have owned two of them and would like to get another one. Yes, slow off line but then you get going pretty good and catch up with the same cars at the next light. Can run 65 on interstate, good enuf for me. My jeep rubicon with 35 inch tires does not keep up with rush hour traffic either, but climbs up and down tough trails like a mtn goat. Just the way things work. Drove a M923a2 back from Nells, AFB 3 Julys ago, did great in 100 degree weather and climbing the mountains on interstate 70 across CO.

 

[Csm Davis]

Tell us about those grand apiece tire that you have found that will hold up to 80 mph and I will be glad to give you all the information you need to run that fast or more and just to be a nice guy and share the first thing you are going to need is a disk brake upgrade.

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[74M35A2]

Wrong vehicle for target objectives.

 

[sawdustnsteel]

Tell us about those grand apiece tire that you have found that will hold up to 80 mph and I will be glad to give you all the information you need to run that fast or more and just to be a nice guy and share the first thing you are going to need is a disk brake upgrade.

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Im sorry, I just reviewed posts. no one has identified any tires or wheels yet. which ones are you talking about or are you assuming tires and wheels from OTHER threads?


BUT since you brought it up. Im trying to find a big rig wheel that will fit on the existing hub. likely a 22" from what Ive seen thus far. Barring finding something that will fit, and or likely to exceed what the axle is capable of, Im also trying to find info on a good replacement for the axles from a big rig donor Truck. which seems the more likely option for comfortable daily driving.

Its not likely to find a tire that will achieve highways speeds AND be worth a **** on off road that I can tell but I DID make a thread about it to find out if anyone else has come across something that does.

dont confuse setting high expectation in trying to find the best mods possible by ASKING what others have found with having any direct information in HOW to make it possible.. the whole point of the thread is to see what others have found out already, what methods they have used that worked, what ideas they have yet to try that are feasible.

its obviously possible to have a dual working vehicle that will do 70 comfortable on highways AND still be viable for off road. I know first hand the Oshkosh MATV does exactly that. however. the thread is about m939 series 5 tons and mods that will achieve the most from that truck base.

 

[Csm Davis]

Im sorry, I just reviewed posts. no one has identified any tires or wheels yet. which ones are you talking about or are you assuming tires and wheels from OTHER threads?


BUT since you brought it up. Im trying to find a big rig wheel that will fit on the existing hub. likely a 22" from what Ive seen thus far. Barring finding something that will fit, and or likely to exceed what the axle is capable of, Im also trying to find info on a good replacement for the axles from a big rig donor Truck. which seems the more likely option for comfortable daily driving.

Its not likely to find a tire that will achieve highways speeds AND be worth a **** on off road that I can tell but I DID make a thread about it to find out if anyone else has come across something that does.

dont confuse setting high expectation in trying to find the best mods possible by ASKING what others have found with having any direct information in HOW to make it possible.. the whole point of the thread is to see what others have found out already, what methods they have used that worked, what ideas they have yet to try that are feasible.

its obviously possible to have a dual working vehicle that will do 70 comfortable on highways AND still be viable for off road. I know first hand the Oshkosh MATV does exactly that. however. the thread is about m939 series 5 tons and mods that will achieve the most from that truck base.

Budd wheels in any size you can think of are readily available, but the only tires tall enough to go 80 mph that you listed are going to be 395/85/20 rated 68 mph and lower and 14.00R 20 and 16.00R 20 rated at 55 mph and lower. The 1000.00 dollar tire was a snide comment that most around here get, because I am 99% sure you won't find a tire that is rated over 68 mph in the size we need. Not trying to rain on your parade but the 80 mph and safe ain't happening. Now 68-70 395's will get you there but you will need to check the sidewalls as some are 55 mph and some 68 mph rated. Now if you still think that we can put all of the engine and transmission and brakes and air filter and exaust mods in one place I invite you to read through all of the 5 ton and 5 ton hotrod and mods forums and post the best ones on this thread. I personally would like to see them on one thread. But you will find way to much for one thread, I am not trying be mean but at some point you will run into different opinions about what's best heck we can't agree which engine is best 855ci or 8.3L.



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[infidel got me]

Agreed with Csm-- all go and no brakes, makes Jack a dead boy!

70 mph in these rigs is waaaay fast enough-- guess I'm starting to show my age.

I keep mine at 65, and that good enuff for me.

 

[simp5782]

At 80. You are going to have a hard time on brakes. Not to mention the suspension is flying by the seat of your butt after the firsy bump throws you into the roof. Some 22.5 tires will hold up to 80 but not all the time. Get your pump built up. Change your compressor wheels. Intercooler. Injectors. Keep it cool around 380. You need the torque cause an A2 wont even break the tires loose on wet grass. If you want to go fast buy a sports car. If you want an 80mph A2. Its gonna last around 10,000miles and your going to wear stuff out. You will also need to obtain a very great insurance coverage in the event your truck exceeds your brakes ability and hit someone.

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[sawdustnsteel]

ok so highway speeds are out. 70 seems doable.. but 65 is sustainable. now back to " best to do" list. ( if you've done mods that worked great or are in trial phase please link them. there is a slew of inventive things being done but spread out everywhere)

on brakes, would Disks be the better route versus standard Rotor? the caliper will have to be attached to a bracket thats welded firmly ( from what I've searched thus far there is aftermarket brackets but not a lot out there about the benefit of disk over standard shoe and rotor.
the removal of air brakes would seem to provide more air for horns etc but the standard tank without pneumatic brakes seems to be a bit much for running a horn on alone. anyone running disks currently have a view?

 

[Csm Davis]

ok so highway speeds are out. 70 seems doable.. but 65 is sustainable. now back to " best to do" list. ( if you've done mods that worked great or are in trial phase please link them. there is a slew of inventive things being done but spread out everywhere)

on brakes, would Disks be the better route versus standard Rotor? the caliper will have to be attached to a bracket thats welded firmly ( from what I've searched thus far there is aftermarket brackets but not a lot out there about the benefit of disk over standard shoe and rotor.
the removal of air brakes would seem to provide more air for horns etc but the standard tank without pneumatic brakes seems to be a bit much for running a horn on alone. anyone running disks currently have a view?

So I take it you don't know big rigs at all. These trucks have drum air brakes and if you upgrade it to disk it will have disk (rotors) air brakes. You will have air brakes no ifs ands or buts. Now I know why you think it will all fit, you have little to no mechanical knowledge and think you can just order all the upgrades and bolt them on using the included instructions. Good luck



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[sawdustnsteel]

So I take it you don't know big rigs at all. These trucks have drum air brakes and if you upgrade it to disk it will have disk (rotors) air brakes. You will have air brakes no ifs ands or buts. Now I know why you think it will all fit, you have little to no mechanical knowledge and think you can just order all the upgrades and bolt them on using the included instructions. Good luck


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actually…. I saw a vendor HERE who makes a bracket for disc brakes for 5 tons. something I didn't think was feasible until I saw the ad HERE. IM pretty sure I did mention I BUILD bikes… not a single thing about building trucks. which would be a reason why I'm asking questions and looking for knowledge plus it was YOU who said " put disk brakes on it" earlier.. and now your being snide because I took you at face value, where you being sarcastic before and figure " what the ****" and just keep on being sarcastic because it makes you feel good?

IF you would like to stop trolling and actually add advice apart from " go build bikes/ don't mod a 5 ton/ etc etc etc" Id appreciate it but saying one thing then coming back after and saying another seems like your trolling.

 

[sawdustnsteel]

. Now if you still think that we can put all of the engine and transmission and brakes and air filter and exaust mods in one place I invite you to read through all of the 5 ton and 5 ton hotrod and mods forums and post the best ones on this thread. I personally would like to see them on one thread. But you will find way to much for one thread, I am not trying be mean but at some point you will run into different opinions about what's best heck we can't agree which engine is best 855ci or 8.3L.

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This is exactly why I started this thread. assuming you guys are the subject matter experts presented to be. then what mods WOULD YOU. recommend for a m939 5 ton. to get the most from the vehicle, both on and off road.


I thought I was rather clear with that. When I started receiving input on what CANT be done I asked which would be better stock or Disk brakes, you decided to take a personal jab at me. ( which is cool, I didn't say I know crap about trucks, I was a Forward Observer in a light infantry Battalion, boots don't need oil.) If your not interested in solutions I get it. but your doing nothing for either of us presenting problems with everything.

so let me ask a more DIRECT series of questions. you can reply with yes or no.

would you focus on engine upgrades like injectors or a better turbo or would you opt for keeping it stock?
would you alter suspension any for a better dual role in on and off road or keep it stock?
would you increase radiator size?
would you install AC? if so would you use a kit or build from specific parts?
would you use Hemmit seats or Mrap or another type?

 

[porkysplace]

This is exactly why I started this thread. assuming you guys are the subject matter experts presented to be. then what mods WOULD YOU. recommend for a m939 5 ton. to get the most from the vehicle, both on and off road.


I thought I was rather clear with that. When I started receiving input on what CANT be done I asked which would be better stock or Disk brakes, you decided to take a personal jab at me. ( which is cool, I didn't say I know crap about trucks, I was a Forward Observer in a light infantry Battalion, boots don't need oil.) If your not interested in solutions I get it. but your doing nothing for either of us presenting problems with everything.

so let me ask a more DIRECT series of questions. you can reply with yes or no.

would you focus on engine upgrades like injectors or a better turbo or would you opt for keeping it stock?
would you alter suspension any for a better dual role in on and off road or keep it stock?
would you increase radiator size?
would you install AC? if so would you use a kit or build from specific parts?
would you use Hemmit seats or Mrap or another type?

Well since just about every one of your questions has been answered at one time or another , why don't spend some time read the approx. 1100 threads on modding at 5 ton and educate yourself , rather than come on this board and try and belittle a member who knows these trucks inside and out because you didn't get instant answers and the answers you did get isn't what you want to hear.

 

[infidel got me]

Sawdustandsteel- lets try to answer some of your questions. These are my opinion, so take it for what its worth.

engine-- turn up your fuel(add a egt temp.sensor) and get a better air filter (k&n) or do air filter mod. to existing housing.

A/c is a no-brainer with you being in Nevada-- cold air outta the vents is always nice.

Hemmit air ride seats are a added comfort-- ask me how I know.

These three things should get you on your way. Season to your taste- turning up the fuel, add a little timing adjustment wakes these 8.3s up a good bit. Again these are only my suggestions, but you will be happy with all three. Hope this helps---------- WILL

P.S. not to be a smart a$$-- but you can find these simple mods. with a google search on top right of page. Let us know how you make out.

 

[Csm Davis]

This is exactly why I started this thread. assuming you guys are the subject matter experts presented to be. then what mods WOULD YOU. recommend for a m939 5 ton. to get the most from the vehicle, both on and off road.


I thought I was rather clear with that. When I started receiving input on what CANT be done I asked which would be better stock or Disk brakes, you decided to take a personal jab at me. ( which is cool, I didn't say I know crap about trucks, I was a Forward Observer in a light infantry Battalion, boots don't need oil.) If your not interested in solutions I get it. but your doing nothing for either of us presenting problems with everything.

so let me ask a more DIRECT series of questions. you can reply with yes or no.

would you focus on engine upgrades like injectors or a better turbo or would you opt for keeping it stock?
would you alter suspension any for a better dual role in on and off road or keep it stock?
would you increase radiator size?
would you install AC? if so would you use a kit or build from specific parts?
would you use Hemmit seats or Mrap or another type?

Thanks Porkysplace, Sawdustnsteel let's back up I want to thank you for your service and I see you are retired and I am going to assume something here and I am sorry if I am wrong but you are medically retired and under 30 and if this is true thank you for your sacrifice. Now back to the thread. Sorry for slamming you a little bit there but you really do need to do more reading, even a bike builder should know the difference between drum and disk brakes but I have heard worse from guys who considered themselves mechanics.
To build your Hulk Hummer (by the way a Hulk version has been done and there are pictures on here) this is what I would suggest you do track down a few members here who live near you and look, ride, and ask questions about their rides. This will help you get a better understanding of what direction you want to go. It sounds like you want one of the big Paris / Dakar service truck / race trucks? It can be done but you will spend huge sums of money to get there and a M939 is probably not what you need to start with.
If you are dead set on M939A2 You need to pick which one you are going to start with? Long wheelbase, short wheelbase, or standard cargo M923A2. Then do you want a winch and what kind of body? These are decisions YOU need to make before we can help you with THE HULK .
You can ask most anyone who has met me on here I will help you get the truck of your dreams if you will try to figure out what you want. This is just like building bikes YOU have to pick out what frame you want hard tail, soft tail, springer front, wide glide? We can't tell you if you want to use ape hangers, or drag bars until You pick out what you want to build.

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[Wildchild467]

I ride in 74M35A2's M925A2 once in a while and that does 67 when the pedal is to the floor and the governor does not let it go any faster than that. Its a good speed/control for the vehicle. I mean its a no brainer... hold it to the floor and the governor doesn't let it go any faster. For me, I wouldn't change that at all. It would use a little help on take off speed. I guess turning up the timing and some higher performance injectors and air filter mod to get it breathing better will help it out a lot. 74M35A2 has a real nice truck and lots of great things about it. The brakes are drum and they work amazing. They could send you through the windshield. I wouldn't change them at all, but again, that's me. His truck starts and runs great. If you could do any mods like timing, injectors, more air, intercooler to help it get better mileage/performance, that would be a plus. I just see the truck for what it is. Its never going to be "fast" like a civilian 4x4, but if you can refine it to get better mileage by making it run more efficient, why not? I would love a M939A2, but my deuce serves me well right now. Heck, you drive a stock deuce at a max speed of 50 for a while, 67mph will seem like a rocket ship. Ask any MV owner, the M939A2 is one of the few stock 6x6 MVs that will get up to modern highway speeds. That enough will make anybody jump for joy.

 

[silverstate55]

It was good meeting you in person at our meeting last weekend; I appreciate your service & your enthusiasm for building a custom 5-ton. Fellow member Grendel has a great ongoing thread about singling out the rear suspension and swapping in an air-ride setup (that we discussed).

I second all of infidel got me's advice above; I've also done all of those and highly recommend the seats swap first & foremost!

74M35A2 has a fantastic 24-volt alternator swap as well as A/C compressor mount for the A2 trucks...I've got both but haven't mounted up a compressor yet.

The drum brakes on these trucks, when properly adjusted, work great...the ABS works very well too, I've had to utilize it a few times due to idiot drivers cutting me off.

As for speed & tires, you can get extra-wide 22.5" commercial polished aluminum wheels and run super single radial commercial tires on them; Soni in New Mexico runs them on his M920 and they look awesome! They won't be quite as tall as the 14.00 or even the 395 military radial tires, but are readily available nationwide and are made for comfortable highway running. The M939-series are night-and-day difference from the M-ATV; I've seen the M-ATV run at Nellis, and WOW! What a vehicle! BUT, I can tell you from personal experience, I don't like my M931A2 going over 65mph...they just aren't made for that. 55mph is its sweet spot and runs best at that speed, especially if you're pulling some weight on level ground.

Members here aren't trying to take personal shots at you; there are a lot of good threads in the 5-ton & 5-ton HR/Modding sections, it is definitely worth your time to search through them and read them. As well, at the bottom of each thread will be a listing for similar threads. If you find some that you like, please Bookmark them by using the "Thread Tools" button at the top of each page. You can even create custom folders to keep better track of your Bookmarks for easier reference. It's well worth the time you take to do so. You can't find better institutional knowledge & experience for these trucks anywhere else.