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New Cummins HMMWV project in the works!

steelsoldiers

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Hi Gang,

As many of you know, I traded my M925A2 for a 1985 M998. It came from a great guy in TX named Rick. It was an interesting 3-way trade where Rick got 19kilo's deuce RV, I got Rick's M998, and Dave 19kilo got my M925A2. The HMMWV is not quite home yet. It is currently in Memphis awaiting some PMCS at a vo-tech school, which is run by another Steel Soldiers member, Brian. Once it leaves Memphis, it will head to WV and into my garage.

The HMMWV is mostly complete and in good shape except for the engine. The current 6.2L has been stripped down and is in bad shape. Since the engine is junk, I will be taking this opportunity to re-power the 998 with a 6BT Cummins. I have a 6BT in the garage on an engine stand waiting for a new home. It is a 190hp/475lb-ft tq P7100 pump engine from a school bus and it has approximately 170k miles on it. It is a runner and shouldn't require any significant mechanical work. I am planning on some new seals, securing the killer dowel pin, swapping in 3k rpm gov springs, adjusting the AFC, installing a more aggressive fuel plate, and swapping in some stage 1 injectors. That should really get that humvee moving. The 6BT is significantly taller than the 6.2L so the 998 will require a 2" body lift to clear the valve covers. I'm not real keen on body lifts, but it worked well for the H1 Alpha and a lot of hard core off road guys run them too. I don't want to hack the body so it's really my only option.

I have several options when it comes to transmission/t-case setups. Option 1 is use a 4BT bread truck adapter with the stock TH400. That's the cheapest option, but no overdrive will be a pain on the highway and the adapter requires tilting the engine or the transmission 10*. Option 2 is use an adapter/flex plate from a company like DeStroked, which will run around $1400 and swap in a 4L80E trans. I'm not a big fan of electronic controls in military vehicle, but I know the late model HMMWV's run them with success. I could also use a manual valve body in the 4L80E, but that will require a lot of shifting and a vacuum source to modulate the line pressure. Option 3 is run a 47RH 4-speed OD trans from a 1994-95 Cummins Dodge Ram followed with a NV241D. The 47RH is hydraulically controlled and would be pretty simple to swap in. I could also use an inexpensive Dodge engine/transmission adapter with this option. It will require new cross-member as well as new drive-shafts like the 4L80E swap. I am leaning this way currently. Option 4 is run an Allison 1000 5-speed, but that would also require an expensive PCM and adapter. The take-out Allisons are pretty expensive compared to the 47RH and 4L80E as well. If money were no object, I would probably go with this option for sheer toughness.

Along with the Cummins swap and drive-train swap, I will also be putting on some 24-bolt rims. The 2" body lift will allow for up to 40" tires, but I will probably run the 37" Goodyears initially. I foresee the Cummins torque wrecking havoc on the stock CV's and geared hubs, so some 12k shafts and hubs will go in at some point. Also, the added weight from the winch I'll be installing and the Cummins will require some heavier springs up front.

This should be a fun project. I can't wait to get the 998 home so I can get the body off of the chassis and start swapping. I'll post more pics and info as things progress. I welcome any feedback about the transmission situation.
 

destroked

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If you're serious about the 5.9, may I suggest a friend of mine in Montana who has done exactly what you're planning for?

Auto World

They are also on facebook if you use that site:
https://www.facebook.com/pages/Auto-World-Conversions/142641585768083?ref=ts


Kenny & his wife Dawna are the owners, the have repowered countless Fords, GM and Hummer models as well. Years ago, I used to work with Kenny. Tell them David referred you to them, they are very good people. Just having a resource in your corner with them is worth the call. Kenny builds motor mounts and accessory brackets in house, he can recommend to you what is worth using and what is going to break. (Lot's of things break, transmissions being the primary frustration with the 5.9's to keep together).
 

steelsoldiers

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Nice. My project HMMWV got a 6.6L Duramax with a PPE turbo kit with an Allison 1000 behind it.
Looking forward to seeing how it comes along!
Nice truck! I considered the Dmax too, but I am a die hard Cummins guy and couldn't resist the challenge.

If you're serious about the 5.9, may I suggest a friend of mine in Montana who has done exactly what you're planning for?

Auto World

They are also on facebook if you use that site:
https://www.facebook.com/pages/Auto-World-Conversions/142641585768083?ref=ts


Kenny & his wife Dawna are the owners, the have repowered countless Fords, GM and Hummer models as well. Years ago, I used to work with Kenny. Tell them David referred you to them, they are very good people. Just having a resource in your corner with them is worth the call. Kenny builds motor mounts and accessory brackets in house, he can recommend to you what is worth using and what is going to break. (Lot's of things break, transmissions being the primary frustration with the 5.9's to keep together).
Good to know, David. Thanks. I have seen Auto World mentioned on the 4BTswaps site quite a bit. I'll give Kenny a call. I figure the tranny will be an issue with this truck. The 47RH trans was OK behind a stock 160hp Cummins, but once guys start tweaking, they start having problems. A built 47RH seems to be one of the favorites among a lot of high-powered Cummins guys so I know it can be built to a good level. I understand that changing out the torque converter and valve body for better units is a good first step.
 

Armada

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A new project build from Chris! [thumbzup] Can't wait for the fun to begin once it gets to your house. Your builds are always well documented and interesting. Looking forward to it!!
 

steelsoldiers

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A new project build from Chris! [thumbzup] Can't wait for the fun to begin once it gets to your house. Your builds are always well documented and interesting. Looking forward to it!!
Thanks Paul. I am excited about it too. I've done a few engine swaps over the years, but this will be by far the coolest one and the most involved. I'll be sure to take lots of pics as usual.
 

TedG

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Welcome to the HMMWV Forum Chris! lol

I look foward to your build! What voltage will you run? What top will you install? Inquiring minds want to know!
 

steelsoldiers

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Welcome to the HMMWV Forum Chris! lol

I look foward to your build! What voltage will you run? What top will you install? Inquiring minds want to know!
Thanks Ted. As you know, it has been a long time coming. I am going to run 24v. The 6BT has a 12v 130A Leece-Neville alternator on it right now and it looks to have the same case as a 24v 100A alternator that I have in my garage. I am thinking about running a 2-man Avenger hard top on it with a M7 pedestal mount in the back :) Although, a 4-man top would be required if I need to take the whole family along with me.

Chris, kenny helped me out a lot with my swap, he is awesome. I got my 4bt swap done, you need to hurry up!! :)
nopics
Thanks Matt. I will give him a call soon. Glad you got your swap done. How do you like it?
 

Elwenil

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What? No NV4500 option? I think a 5 speed Cummins HMMWV would be pretty cool. :cool:

No matter what you choose it's a very cool project Chris. Good luck with it!
 

steelsoldiers

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Thanks Westy! ;)

Lanty, I actually thought about a standard swap just to be really different, but the NV4500 shift tower would be too far back. I suppose I could run a ZF6 since the shift tower is about 4" closer to the engine. I'll settle for a built slush box though.
 

Nonotagain

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Chris, some of the local Mudders are running warmed over Allison 1000 transmissions with Suncoast 6 speed conversions to get more top speed and lower the engine rpm.

I'd rather have the option to run down the highway 65-70 mph with the Allison than take a chance with the other transmissions.
 

steelsoldiers

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Here are some pics of the 6BT. I sure hope I can squeeze that mammoth air compressor in there :) The Ford valve cover emblem and engine data plate will really confuse folks. The engine came with a SAE #2 tranny adapter on it with saddle mounts and a front mount. It's a beast! I'll be selling the adapter, mounts and starter to recoup some cash. I think I'll bump the timing to around 16*.
 

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