Best mechanical transfer case with 2WD option for HMMWV

[TOBASH]

1987 Slantback with 6.2 and currently with TH-400.

So, about to do a lot of stuff, and I figured if I'm gonna do a Bowtie 700R4 swap to my Slantback, I might as well consider swapping in a 2WD capable transfer case.

I want to do highway vacation driving, so 2WD should help with MPG relief.

What transfer cases are mechanical shift and suited to the job, and what will I need to do to adapt them to my 1987 HMMWV Slantback? Will I need new console shifter? Adapter plates? Input / Output shaft mods or adapters or replacements? That kinda' stuff.

[If this is the wrong forum, MOD's please forgive me and throw the post where you think it best fits.]

EDIT - January 14, 2023. I’ll save you some time reading the thread. Because we can’t install wheel hub locks and our whole wheel assemblies roll to allow for the inboard brakes, the 2WD option saves no energy and is a fool’s errand.

 

[m16ty]

I don’t know much about the HMMWV platform, but I’d say a NP208 should work fine. If you want something stronger, go with a NP205.

The NP208 gets a bad rap, being a aluminum case chain drive, but the fact is short of hard core off-road, people rarely have problems with them.

 

[ken]

Here is something to consider. If you install a 2WD capable transfer case you will still have the front axle and hubs turning. There is no lockout hub or central axle disconnect for the Humvee or H1. Because the same componets will continue to turn just as the are now, you will not see any improvement in fuel economy. The only difference is you will be able to do burnouts with the rear tires. If you have enough horsepower that is.

 

[Dock Rocker]

Here is something to consider. If you install a 2WD capable transfer case you will still have the front axle and hubs turning. There is no lockout hub or central axle disconnect for the Humvee or H1. Because the same componets will continue to turn just as the are now, you will not see any improvement in fuel economy. The only difference is you will be able to do burnouts with the rear tires. If you have enough horsepower that is.

He is right. With no way to disconnect the hubs you will still be turning all the same running gear no matter what you do with the transfer case.


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[TOBASH]

Yeah, I guess hub disconnects might be impossible.

Thanks guys!

 

[Skrilex]

The NP241 is a direct swap for the NP242 and it’s a 2wd t case.

 

[TOBASH]

The NP241 is a direct swap for the NP242 and it’s a 2wd t case.

Excellent info. Thanks.

New Issue...Forgot about need to unlock hubs.

Hub lock/unlock would be the next "thing".

 

[Skrilex]

That one is a lot tougher

 

[TOBASH]

That one is a lot tougher

Yeah. LOL. Seems like a fool's errand. Me thinks I'm gonna just let this one go.

Thanks for your reply though!

 

[McSpeed]

Are you getting a 700R4 already configured with the larger output spline for the Humvee stock transfer case? That is more costly.

If you are going to use another transfer case, you could consider finding one as a donor 700R4 already mated up to a stock GM truck configuration that would take the smaller input shaft.

Depending on what you are doing with the truck that may suffice and give you more flexibility on transmission build cost and variants on the transfer case.

 

[TOBASH]

Are you getting a 700R4 already configured with the larger output spline for the Humvee stock transfer case? That is more costly.

If you are going to use another transfer case, you could consider finding one as a donor 700R4 already mated up to a stock GM truck configuration that would take the smaller input shaft.

Depending on what you are doing with the truck that may suffice and give you more flexibility on transmission build cost and variants on the transfer case.

Excellent thoughts. I had not considered. Thanks.

There might be an issue with mating up the new transfer case to the stock shifter due to the 2 wheel extra option, I guess, unless I configure the stock shifter to bypass that setting.

 

[DREDnot]

Sounds like a 700R4 with the HD output mating to the stock T-case is the way I'd pick to go when its time.

 

[McSpeed]

I've been giving this swap a lot of thought. I've done 3 speed to 4 speed autos in cars where I went to bowtie overdrives and got shifter mods to accept the new pattern in the old unit. The one they make for my 69 Camaro is awesome and looks and acts stock. This is also fairly cheap for the cars. I've been looking at the humvee and see that I can get a 4L80E shifter...but they are MONEY. This build for me is about the fun and adventure and keeping the spend on the low, so $500 or more for a shifter on top of the trans and other parts is a buzz kill. I don't want to run the computer for a 4L80E. So, the 700 is the alternative. But my research shows the output shaft is the wrong spline to turn the Humvee TC. Advanced adapters has one, but it is like $500 for parts. You still need then to build or buy (around $100) a 4th gear lock-up device for the 700.

It makes a complete donor look really nice, but we are talking 30+ year old donors - they are hard to find in good shape. So, it is a donor and a rebuild...and then still figure out the shifter. I love this stuff, but at some point you have to weight it all out. There is a scarp yard in Alabama that sells complete 6.5 turbos with 4L80E trans and TC as pull outs for around $850. For that, making my 6.2 a better all around performer PLUS going ahead and doing the computer swap starts making sense...but I still have to track down the shifter lever assembly.

 

[McSpeed]

You need to contact Predator or somebody that has been doing the Duramax swaps since they often put the entire drive train in - they might know how to best manipulate or replace the shifter to work - however...those might be fully electric and therefore only require putting a switch in the interior instead of an actual linkage.

 

[Dock Rocker]

Advanced adaptors makes anything you need to go from the 700r to just about any transfer case on the planet. They would be very helpful


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[TOBASH]

Advanced adaptors makes anything you need to go from the 700r to just about any transfer case on the planet. They would be very helpful


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Excellent point and thanks. That info will come in handy!

 

[Dock Rocker]

If you are on Facebook, the Hmmwv owners group has a guy that sells a drop in kit for the 700r4 and the 218 or the 242.


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[Sharecropper]

Bowtie Overdrives will build a K-case 700R4 with the correct output shaft already installed. Level 2 rated at 450 hp. Call Chris Gardner there and tell him what you want. I just bolted mine behind my P400 and it is slick. Photos toward the end of my rebuild thread.

 

[TOBASH]

Bowtie Overdrives will build a K-case 700R4 with the correct output shaft already installed. Level 2 rated at 450 hp. Call Chris Gardner there and tell him what you want. I just bolted mine behind my P400 and it is slick. Photos toward the end of my rebuild thread.

Excellent information and making me think BowTie is gonna be the way I'm gonna go.

Looks like your still in the midst of your project. It is an excellent read!

Did BowTie help with the TM wire and adapter plate, and did they help with sourcing a 4 speed shifter?

 

[Sharecropper]

[QUOTE
Did BowTie help with the TM wire and adapter plate, and did they help with sourcing a 4 speed shifter?[/QUOTE]
No, Bowtie is strictly a transmission builder. The original TH400 shifter in my 1984 M1028 will bolt right up to the 700R4 with no issues. However for a HMMWV swap, I am confident that you will need to do some custom fabrication. No reason it will not work. You will just need to think outside the box a little.