M998 upgrade

[Don Vito]

Hello all, I am looking for some advice on the hmmwv, I don't personally own one yet, but am very serious about buying one. I have some questions/concerns about the drive-train for the truck. Firstly, although I greatly appreciate the unique nature of the stock hmmwv engine, when i buy one, I will be swapping the engine out for either a cummins or a duramax. I will be swapping the engine out as I will be using the truck to occasionally haul a backhoe on a gooseneck (GVWR 30,000lbs) , so i'm looking for the reliable and easily serviceable engine as well as the increase in horsepower (be able to reach 80mph) and torque (max tow load @ 35,000lbs). I'm sure someone will recommend for me to simply get a civy dually or something else, but I am set on the hmmwv since Ive always wanted one and REQUIRE its off-road capabilities. Now my questions are;

Where could I find a larger rear differential, with say a 4.15 gearing, that will fit where the stock differential is?

Once I upgrade the drive-train of the truck, will I need to swap all the tie-rods and axles to be able to handle the increase in torque?

Where can I find (or what can I do) to ensure the unique brake system of the truck can handle the added weight of a towed load?

Is there any transmission and/or transfer case you'd recommend I use for the set-up i'm describing (speed is important, but not nearly important as torque)?

If you guys could give me some feedback on my questions and what I plan to do, I'd really appreciate it.

 

[DatGuyC]

Hello all, I am looking for some advice on the hmmwv, I don't personally own one yet, but am very serious about buying one. I have some questions/concerns about the drive-train for the truck. Firstly, although I greatly appreciate the unique nature of the stock hmmwv engine, when i buy one, I will be swapping the engine out for either a cummins or a duramax. I will be swapping the engine out as I will be using the truck to occasionally haul a backhoe on a gooseneck (GVWR 30,000lbs) , so i'm looking for the reliable and easily serviceable engine as well as the increase in horsepower (be able to reach 80mph) and torque (max tow load @ 35,000lbs). I'm sure someone will recommend for me to simply get a civy dually or something else, but I am set on the hmmwv since Ive always wanted one and REQUIRE its off-road capabilities. Now my questions are;

Where could I find a larger rear differential, with say a 4.15 gearing, that will fit where the stock differential is?

Once I upgrade the drive-train of the truck, will I need to swap all the tie-rods and axles to be able to handle the increase in torque?

Where can I find (or what can I do) to ensure the unique brake system of the truck can handle the added weight of a towed load?

Is there any transmission and/or transfer case you'd recommend I use for the set-up i'm describing (speed is important, but not nearly important as torque)?

If you guys could give me some feedback on my questions and what I plan to do, I'd really appreciate it.

You want to tow 35k at 80mph in a HMMWV. Must be some pretty good drugs going around down there in Texas.

 

[Don Vito]

You want to tow 35k at 80mph in a HMMWV. Must be some pretty good drugs going around down there in Texas.

I'm sorry, maybe I should've been more clear. I want to be able to tow 35k @ 65mph and be able to reach speeds of 80mph unloaded. After an engine swap and rear-differential swap, I dont see why this would be hard to accomplish. If you could explain why it would seem like a stretch, I'd appreciate that.

 

[DatGuyC]

I'm sorry, maybe I should've been more clear. I want to be able to tow 35k @ 65mph and be able to reach speeds of 80mph unloaded. After an engine swap and rear-differential swap, I dont see why this would be hard to accomplish. If you could explain why it would seem like a stretch, I'd appreciate that.

You want to tow 35k at *65mph* in a HMMWV. Must be some pretty good drugs going around down there in Texas.

I'm sorry but I don't even know where to begin. You want to tow more weight than even the newest large pickups were designed to tow with a truck that is rated at a max towed capacity of 3k pounds. I'm not an automotive engineer, but literally every part of the HMMWV would have to be redone to accommodate that. The driveline, frame, axles, suspension, brakes, literally everything. Sure it could be done, but you would end up with something that is no longer a HMMWV so then whats the point?

 

[whistlepig]

A Humvee is not what you seek. With the speeds and weight you want, a civilian truck is what you need. What happened to your 5 ton 6x6 plan from last month?

 

[springer1981]

You have picked the wrong vehicle for the application. It will never do what you are asking safely as it was never intended for that. In stock form is has a towing capacity of around 4000 lbs. I suspect you don't understand the drivetrain at all. The hubs are all gears at 1.91:1, if you changed the differential to 4.15 you would have an effect ratio of 6:1? The current Diff ratio is less than 3:1 and it's top speed is 55mph MAXED out. It is happiest at 40-45. You would be reducing that significantly.

Your plan it totally flawed in every way. If you want an HMMWV for fun or 4 wheeling or what have you, then go for it. It will not do what you are asking.

 

[Don Vito]

A Humvee is not what you seek. With the speeds and weight you want, a civilian truck is what you need. What happened to your 5 ton 6x6 plan from last month?

My 5 ton plan is still my primary plan and I'm getting closer to making the purchase, I just wanted to see if the hmmwv could do the bulk of my work and save me a few headaches in CMV paperwork. BUT, since I'm getting the very strong impression that it cannot do what Id need it to do (and yes I do not know all that much about hmmwv's), ill likely stick to the M916A1 or M931. But I was hoping to see if, with modifications, the hmmwv could do the job and I wanted you all's opinion. I read somewhere on the forum that someone was able to pull something like 56k with a hmmwv? It surprised the logic out of me. Maybe I read that post wrong, but it definitely made me curious enough to ask for feedback

 

[TOBASH]

My 5 ton plan is still my primary plan and I'm getting closer to making the purchase, I just wanted to see if the hmmwv could do the bulk of my work and save me a few headaches in CMV paperwork. BUT, since I'm getting the very strong impression that it cannot do what Id need it to do (and yes I do not know all that much about hmmwv's), ill likely stick to the M916A1 or M931. But I was hoping to see if, with modifications, the hmmwv could do the job and I wanted you all's opinion. I read somewhere on the forum that someone was able to pull something like 56k with a hmmwv? It surprised the logic out of me. Maybe I read that post wrong, but it definitely made me curious enough to ask for feedback

It is a sign of poor understanding of the mechanics of pulling a load for anyone to imagine a 5-6K vehicle might be safe at 65MPH pulling 35K.

In another post you indicate you might just swap out the rear diff to make your vehicle move at 80MPH. This is a 4WD vehicle with front and rear diffs, requiring 2 diff changes. The tallest gears you will find easily accesible are 2.56 or so IIRC.

Duramax swap kits are upwards of 12K without the engine. Fitting a Cummins is something I have always hated and continue to hate. You want a Cummins in order to pull, buy a Dodge 3500.

You will need at least a 4 speed tranny, and probably an Allison to do any real pulling. That won't be cheap.

I'm not sure you understand the basics of pulling, the basics of choosing a vehicle to pull, or the basics on how to build a vehicle on a correct platform.

I welcome you to the forum, (and I don't want to frighten you off), but I suggest you lurk around and read prior to making overly ambitious statements about what you are looking to build.

T

 

[infidel got me]

Why

 

[TOBASH]

Why

Because Friday is Tin Foil Hat Day?

[Why in reference to what IGM?]

 

[98G]

Hello all, I am looking for some advice on the hmmwv, I don't personally own one yet, but am very serious about buying one. I have some questions/concerns

If you guys could give me some feedback on my questions and what I plan to do, I'd really appreciate it.

You hear them called a 1 1/4 ton truck.

You know that civvy 1 ton trucks pull this type of load.

Therefore it should not be that much of a stretch.

***nothing could be further from the truth****

The performance of a hmmwv is far closer to a jeep wrangler than it is to a heavy pickup truck. There's not a single component suitable for use in your proposed application.

The ideal vehicle for your application is a heavy diesel pickup. Preferably heavier than 1ton. (Think 4500 or 5500).

If you're wanting to do this with a military vehicle then the 5ton trucks are for you. They're going to be SLOW and crude in comparison to a civvy pickup truck.

My opinions come from first hand experience. I currently have 5ton trucks, a HMMWV, a jeep wrangler, a 1ton truck with a Cummins, and a heavy gooseneck.

There's no combination of circumstances and modifications that could induce me to even consider a hmmwv as the prime mover for a heavy gooseneck.

 

[infidel got me]

Because Friday is Tin Foil Hat Day?

[Why in reference to what IGM?]

Why would you even consider answering this REDICILOUS post !!!!!! THAT'S WHY

 

[TOBASH]

Why would you even consider answering this REDICILOUS post !!!!!! THAT'S WHY

Understood, and in retrospect...agreed.

 

[Crazyguyla]

The stock engine will do 80 mph easily, the military purposely detuned the engines to keep the speed down. I used to work on civilian Hummers/H1's and a 4 door "wagon" as they're labled will do 110mph like skating on ice, so smooth.. I think the detuning involved the retarding if mechanical timing (crankshaft to camshaft) and injections pump timing. Same drivetrain and gearing..

 

[Retiredwarhorses]

The stock engine will do 80 mph easily, the military purposely detuned the engines to keep the speed down. I used to work on civilian Hummers/H1's and a 4 door "wagon" as they're labled will do 110mph like skating on ice, so smooth.. I think the detuning involved the retarding if mechanical timing (crankshaft to camshaft) and injections pump timing. Same drivetrain and gearing..

this is even funnier then the OP...but heck, WTF do I know....

 

[sue]

this is even funnier then the OP...but heck, WTF do I know....

I say press on, sounds totally doable.
it’s a little known fact that the
heavier load you carry and the faster you go
the better fuel mileage you get.
But the govment keeps deleting it from
the intronet, example, try to find out
why real smarter fellers line the tinfoil
hat with lead based paint.!!

 

[diesel dave]

You just can’t make this stuff up! I gotta make some popcorn!

 

[TOBASH]

Plenty for everyone.

Let me know who wants butter.

 

[ken]

With that kind of weight I can see the spindles leaving the geared hubs in a hurry. Not to mention all the snapped half shafts while trying to stop at a red light. Although there isn't many red lights in Premont and it's really flat terrain there. That is WAY too much weight to even risk out on US281.

 

[simp5782]

Why not save money and out a swb standard cab 1 ton or 3/4 truck with the correct power train and fab the little hmmwv body to it. Rather than spending 20k in time.parts and cuss words to build something that would not work.

Putting a body on something that has no creature comforts and are cramped to be in is moronic if it's only about looks

It used to be cool to have a hmmwv 5yrs ago. Now people just get my condolences for having one