HUMVEE Ultra4 (KOH) Build?

[jrtoffroad]

Hey guys,

Not sure if anyone here is familiar with Ultra4 racing, but this is an offroad race series that combines high speed desert or short course with rock crawling. The most famous race in the series is King Of the Hammers (KOH). I've been racing in Ultra4 since 2012. I started with a highly modified jeep, then moving to a rear engine IFS buggy. I recently listed my buggy for sale and am considering building a new rig based on a humvee. The goal would be to utilize as much of the humvee as possible to keep costs down and have decent availability of replacement parts. My current buggy is amazing, but it's single seat and very expensive to operate since so many of the parts are custom or just generally very high end.

Some of the VERY rough specs for my Humvee build are:
-Stock Humvee portals
-Stock 12k axle shafts (maybe)
-Stock Diffs with 3.08 gears and Detroit or Grizzly lockers (maybe)
-Stock 242HD T-case
-Custom HD drivershafts with 1350 joints
-Highly build 4l80e trans with RMVB
-Procharged LS3 V8
-Near stock suspension geometry with custom upper and lower arms using uni-balls
-Coil over shocks with 3.5" or 4" bypasses and air bumps
-Strock Alpha steering with HD custom tie-rods (hydro assist need TBD)
-Stock brakes
-Narrowed body (~20-24") and shortened WB (~12")
-40" tires
-Race weight <5500lbs (i'm hoping for close to 5k, but we'll see)

I currently own 4 humvees, one of which is an M1152 that I would use as a base for this build. I've been very impressed with humvee durability, but am concerned about whether the diffs and stock 12k axles can really take the abuse. Has anyone here broke a ring and pinion in their humvee? If so, what were the conditions? How about the 12k axles? I know plenty have broke the 10k or earlier stuff, but how well do the 12k's hold up.

Custom axles and diffs aren't out of the question of course, but I'd love to use what's there. I've never had an issue with these parts in either of my M1123 wheeling rigs I've had, but Ultra4 is a whole new level of abuse. I'm a little worried about the front diff since it runs on the coast side of the gear, but the reduced torque from the portals seems to really help everything survive.

Here's my IFS rig:



1100hp of procharged hemi goodness.

 

[Mullaney]

Hey guys,

Not sure if anyone here is familiar with Ultra4 racing, but this is an offroad race series that combines high speed desert or short course with rock crawling. The most famous race in the series is King Of the Hammers (KOH). I've been racing in Ultra4 since 2012. I started with a highly modified jeep, then moving to a rear engine IFS buggy. I recently listed my buggy for sale and am considering building a new rig based on a humvee. The goal would be to utilize as much of the humvee as possible to keep costs down and have decent availability of replacement parts. My current buggy is amazing, but it's single seat and very expensive to operate since so many of the parts are custom or just generally very high end.

Some of the VERY rough specs for my Humvee build are:
-Stock Humvee portals
-Stock 12k axle shafts (maybe)
-Stock Diffs with 3.08 gears and Detroit or Grizzly lockers (maybe)
-Stock 242HD T-case
-Custom HD drivershafts with 1350 joints
-Highly build 4l80e trans with RMVB
-Procharged LS3 V8
-Near stock suspension geometry with custom upper and lower arms using uni-balls
-Coil over shocks with 3.5" or 4" bypasses and air bumps
-Strock Alpha steering with HD custom tie-rods (hydro assist need TBD)
-Stock brakes
-Narrowed body (~20-24") and shortened WB (~12")
-40" tires
-Race weight <5500lbs (i'm hoping for close to 5k, but we'll see)

I currently own 4 humvees, one of which is an M1152 that I would use as a base for this build. I've been very impressed with humvee durability, but am concerned about whether the diffs and stock 12k axles can really take the abuse. Has anyone here broke a ring and pinion in their humvee? If so, what were the conditions? How about the 12k axles? I know plenty have broke the 10k or earlier stuff, but how well do the 12k's hold up.

Custom axles and diffs aren't out of the question of course, but I'd love to use what's there. I've never had an issue with these parts in either of my M1123 wheeling rigs I've had, but Ultra4 is a whole new level of abuse. I'm a little worried about the front diff since it runs on the coast side of the gear, but the reduced torque from the portals seems to really help everything survive.

Here's my IFS rig:

View attachment 891776

It's for sale for $125k if anyone is interested. 1100hp of procharged hemi goodness.

.
That is an amazing buggy!
Not so sure that kind of adventure is for me - but DANG it is cool!

I don't think I could give you any worthwhile comments on the HMMWV durability - but I'd bet some of the other guys will jump in here and throw down some opinions...

 

[Mogman]

I guess my question would be what are you going to compete against?
Make sure you keep us updated, this definitely belongs in the HMMWV mods forum.

 

[NDT]

Look into the Rod Hall suspension set up equipped on GMV HMMWVs. Eastern Surplus has these trucks for sale. Basically set up for Baja as is.

 

[Mogman]

I would not think the mid 5K range would be too tough, my bare bones M998 with a Duramax/A1000 weighs in at 5,300.
One of the possible issues is narrowing the body, as is the drivers feet are outside the frame, not allot of room to narrow.
This will be interesting for sure.

 

[Vapor Trail]

I’ll be there next year so hope to see you in your new rig!

 

[Mogman]

The AMC 20 diffs have an 8 7/8 ring gear and are about as tough as a ford 9", the HMMWV of course has an aluminum housing so I am not sure if that would lower the durability or not.
I built a Duramax/Allison/MP T/C powered HMMWV so it has part time FWD and I have beat on it as hard as I can on the street with tunes up to 475HP in two wheel drive and 7K and 10K half shafts and have not been able to break anything (except blowing out the Autozone half shaft boots at post 3 digit speeds) much to the chagrin of all those "experts" that said "everything will break", of course that is nothing compared to what you have planned.
You may want to cryo some of the parts as I understand that is a very economic way to strengthen steel.
Please keep us up to date on your build with allot of pictures!!!
I have read some guys are running HMMWVs at Baja.

 

[jrtoffroad]

Thanks for all the feedback guys!

I would like to build this so it could compete in either 4500 or 4400 classes with just a shock & tire change. 4500 is stock modified which limits tires to 37's and shock diameter to 2.5" (also requires resemblance to a production vehicle and a mechanical steering connection which won't be an issue for my build). 4400 is unlimited, so buggy I'm racing now.

The Rod Hall stuff is neat, but not quite what I'm looking for. I need something extremely robust as the vehicle will be smashed through rocks at speed. The stock sheetmetal lower control arms probably wouldn't stand a chance. Also, I'll need custom valving and spring rates since my final weight will be hopefully lighter than a stock HMMWV (and MUCH lighter than an H1).

For now I'm planning to give the AMC 20's a shot and see how they do. Might as well break something before I spend a bunch of money on something else. Although the 9in is only a tiny bit larger in stock form (they make up to 10" gears for them), the high hypoid offset and addition of a 3rd pinion bearing really add a lot of strength. With that said, up front I would not choose a 9in since it would be on the coast side of the gear when going forward just like the 20. I'd need to start with a reverse rotation gear like a high pinion dana 44, 8.8, dana 60, etc. to be on the driveside. I don't think the AMC 20's are weak though. If I remember, I think the pinion is quite a bit beefier than a dana 44. For gears I'll probably go with the stock 3.08's to start. Might move to a 3.31 eventually, but we'll see.

Cryo treatment is not a bad idea. I've done that to a few parts before. Can't really say if it did much or not, but it's a nice piece of mind.

 

[jrtoffroad]

I'm very excited to get going on this, but really need to sell my IFS car 1st...

 

[Vapor Trail]

XHP makes a setup like this with coil overs and billet control arms

 

[jrtoffroad]

XHP makes a setup like this with coil overs and billet control arms

I did see their site. Thanks for the recommendation. Neat stuff, but more than I care to spend. At that price I'd prefer to build my own. Especially because it looks like I'd need to modify their design to accommodate the coil over and bypass shock configuration I'm planning.

But, it might be worth talking to them...

 

[jrtoffroad]

Got a few parts together this week:
-Built 4l80e
-Billet converter
-Winters gated shifter
-LS3 (Ive had this guy for a little bit, trying to decide if I want to stroke it out to a 415 - which I already have a crankshaft for, or leave the bottom end basically stock)
-40 gallon fuel cell and pump setup
-40" Mickey Thompsons on Raceline beadlocks
-Also got a couple nrg seats, but not sure I'm happy with the fitment, might do with something else.
-I also acquired a behemoth drivetrain aluminum case twin stick 205. not sure if I want to run this or the humvee 242...

 

[jrtoffroad]

No exciting updates yet. I've been trying to work through some projects to make room for this one. I've done a little measuring on the body. The narrowing is going to be a very interesting task, but I'm anxious to start cutting.

How dangerous is the CARC paint? With all the cutting, grinding, and welding I'll be doing, I'm wondering if I should have this thing sand blasted to get the paint off, or if just using a respirator while manually removing (wire wheel maybe?) will suffice?

 

[Mullaney]

No exciting updates yet. I've been trying to work through some projects to make room for this one. I've done a little measuring on the body. The narrowing is going to be a very interesting task, but I'm anxious to start cutting.

How dangerous is the CARC paint? With all the cutting, grinding, and welding I'll be doing, I'm wondering if I should have this thing sand blasted to get the paint off, or if just using a respirator while manually removing (wire wheel maybe?) will suffice?

.
The VA is dealing with veterans who were exposed.
Here is some of the information that is posted on their website.

The Sherwin-Williams MSDS (safety data) sheet is attached below as well.

COPY-PASTED from the VA

CARC Paint

CARC (Chemical Agent Resistant Coating) is a paint used on military vehicles to make metal surfaces highly resistant to corrosion and penetration of chemical agents.

Inhaling CARC during the painting and drying process can be harmful. Dry CARC poses no hazards, except during welding or sanding.

If you are concerned about exposure to CARC paint during your military service, talk to your health care provider or contact your local VA Environmental Health Coordinator to help you get more information from a health care provider.

How Veterans may have been exposed to CARC paint
Gulf War Veterans who painted combat vehicles and equipment during their military service may have been exposed to CARC paint or fumes without adequate respiratory protection.

Other Veterans who painted tanks, armored personnel carriers, and other motor pool equipment may have been exposed. Some civilian units and support units may have been exposed.

Learn more about exposure to CARC paint from the Army Public Health Center.

Health problems associated with CARC paint
Paint fumes present the most potential risk to users especially when CARC is spray painted, rather than applied with a brush or roller.

CARC paint contains several chemical compounds that can be hazardous when inhaled or exposed to the skin:

• Isocyanyte (HDI) – Highly irritating to skin and respiratory system. High concentrations can cause: itching and reddening of skin; burning sensation in throat and nose and watering of the eyes; and cough, shortness of breath, pain during respiration, increased sputum production, and chest tightness.
• Solvents – Inhaling high concentrations can cause coughing, shortness of breath, watery eyes, and respiratory problems, including asthma
• Toluene diisocyanate (TDI) – High levels released during the drying process can cause kidney damage.

Health concerns?
If you are concerned about health problems associated with exposure to CARC paint during your military service, talk to your health care provider or contact your local VA Environmental Health Coordinator to help you get more information from a health care provider.

 

[jrtoffroad]

Front and rear detroit lockers ordered. In a little change of plans, I'm going to take this rig wheeling in Moab at the end of the month. So, also ordered some Armada springs and spring spacers (temporary suspension upgrade). Going to throw in the lockers, springs, quick hockey puck body lift, trim the fenders, install the 40's and go beat on it. When I get back I'll start cutting the body and pull the drivetrain.

Also means I need to get this turbo diesel up and running and find all the other stuff keeping it from driving. Oh well, plenty of time.

 

[jrtoffroad]

This thread is in desperate need of some pics. I'll get some soon.

Last night I picked up a set of 2.5" Fox Shocks with Airbags on them. Very excited to give these a shot and see how they ride. I've really wanted the ability to adjust ride height and weight capacity. These were apparently a prototype for a military application, although that's all I know. Probably not something I'll keep on for racing, but who knows...

 

[jrtoffroad]

The internet is wrong!

Everywhere on the internet it says the carrier break for the AMC 20 is 2.73/3.07. This is NOT correct (at least for a Humvee) and just bit me. The 3.08 gears in the Humvee diffs uses the same carrier as the 2.73 and down. SO, up to a 3.08 gear you'll want a diff listed for 2.73 and down gears.

With only a few days until Moab I now either need to find different lockers, or go to a 3.31 gear set, which is a little lower than I was hoping. Also, it's hard to find a locker in stock for the 2.73 and down gears. Not even sure if Eaton is still making the detroit in that size.

 

[Mogman]

The internet is wrong!

Everywhere on the internet it says the carrier break for the AMC 20 is 2.73/3.07. This is NOT correct (at least for a Humvee) and just bit me. The 3.08 gears in the Humvee diffs uses the same carrier as the 2.73 and down. SO, up to a 3.08 gear you'll want a diff listed for 2.73 and down gears.

With only a few days until Moab I now either need to find different lockers, or go to a 3.31 gear set, which is a little lower than I was hoping. Also, it's hard to find a locker in stock for the 2.73 and down gears. Not even sure if Eaton is still making the detroit in that size.

All the carriers for the HMMWV are the same part number so as you found out there is no split in that application.
EDIT, I wonder if the civy 3.08 gears are different?

 

[Valley Rock]

Just a quick check on eghey shows me several options fro the 20, Spartan, Lokrite and Detroit Locker .
I didn't dig into ratio selection on the Detroit, but stuff is out there for sure .

Seems like maybe rigging up cutting brakes (poor mans locker) for the rear would me quicker/simpler for Moab rather than stressing over gears and having your rig set in a puddle of oil when fun time shows up .

Or just roll out the Lincoln and make that rear or both a one piece carrier .

 

[Valley Rock]

Oops, forgot pics for proof

.