700r4 conversion info

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driveatank.com
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700r4 conversion info

Post by driveatank.com » Tue May 22, 2012 7:39 pm

Hey Guys, I did a search but found little info. I have been exploring the 700r4 oprtion for a M998. I have a truck we only use on off road trails, around the yard etc and high range is a little high and low is a little low. I think the big OD in the 700 with the T-case in low would be perfect, and my favorite.....mechanical.

SO....Does any one have any info on the swap? Like T-case options? There are plenty of 6.2 chevys with the 700 but i'm currious about t-cases or if any one has done the swap. Things like cross member, fuel tank etc.

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Ted Gates
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Re: 700r4 conversion info

Post by Ted Gates » Fri May 25, 2012 1:50 pm

A 700R4 connects nicely to a 241 Tcase which allows 2 wheel drive. Use a military 4 speed shifter and fab up some simple brackets (mostly TH400 and 4L80E stuff) to use all 7 positions (P-R-N-OD-3-2-1). The tcase will sit closer to the fuel tank (rub) so you will need to drill two new holes in the cross member towards the driver's side to allow clearance. Then you need a manual torque converter lockup switch and a speedo adapter to conver the 241 signal to a speedo. The 700R4 is borderline weak for the hmmwv but if you do not tow or do not do too much off roading, it can be a good o.d. tranny. They can go fast (over 70) and in 2 wheel drive, burnouts are fun! :D

I have only owned a hmmwv with this setup and it has been awhile so if you want more details....sorry those brain cells are gone! :wink:

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Re: 700r4 conversion info

Post by driveatank.com » Sun May 27, 2012 3:57 pm

Awsome,

That is exactly what I was looking for. Still checking out the options at this point.

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Re: 700r4 conversion info

Post by ida34 » Thu Jun 13, 2013 2:28 pm

Is this the HMMWV that can be seen during the Larry the Cable Guy show?

eisenhe
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Re: 700r4 conversion info

Post by eisenhe » Mon Sep 28, 2015 7:11 pm

I'm in the process of doing this, but I'll summarize what I've got so far.
The 3L80 aka Turbo 400 transmission was the first HMMWV transmission; it had no parking pawl. 3L80 means three gears, strength rating 80.
The 4L80E is the later version. 4 gears, still strength rating 80, and electronically controlled.

The 700R4 aka 4L60 has 4 gears and strength rating 60. Its output shaft is smaller and its tail bolt pattern is different. However, when installed in 4x4 pickups the tailshaft adapter makes it a 6-bolt output like the HMMWV transfer case input. But not exactly the same. Note that while the Turbo 400 has a six-bolt output pattern, it is offset (twisted) slightly from the NP218 six-bolt pattern. Also, at least one bolt does not line up with the holes.

Early HMMWVs had the NP218 transfer case; later models have the NP242. Compared to Chevy 4x4 pickups and the CUCV, the biggest difference is that the front output shaft comes out on the drivers' side; the civilian ones come out on the passenger side. CUCVs and pickups used the NP208 tcase. Of note is the fact that the transfer case input gear exterior dimensions are the same for the NP208 and NP218.

What I did was to swap the NP208 input gear into the NP218 transfer case; this matches the 700R4 output shaft with the NP218 tcase input. Next I bought an Advance Adapters part 51-6901, adapter for the 700R4 to NP218. This will bolt to the 700R4 tail, and the HMMWV standard transmission adapter (part 12339134) will bolt to it and has the transmission support underneath it. I haven't bolted them together and installed them yet, but it looks like the transmission support will be in the right place. I will also need a new shifter with the Park position and maybe even OD. We shall see!
1986 HMMWV M998A0 sn20423 working on 6.2 install


eisenhe
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Re: 700r4 conversion info

Post by eisenhe » Mon Oct 12, 2015 4:53 pm

They're bolted together -- fit is perfect. Needed some smaller head bolts to mate the adapter to the trans; used some header bolts from Napa. Ready to put the drivetrain back in. :)
1986 HMMWV M998A0 sn20423 working on 6.2 install

eisenhe
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Re: 700r4 conversion info

Post by eisenhe » Tue Nov 03, 2015 6:12 pm

They're installed, and the fit is perfect. Transmission crossmember bolts right in with no adjustments needed. Highly recommended!
1986 HMMWV M998A0 sn20423 working on 6.2 install

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dilvoy
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Re: 700r4 conversion info

Post by dilvoy » Mon Nov 30, 2015 2:02 pm

eisenhe wrote:They're installed, and the fit is perfect. Transmission crossmember bolts right in with no adjustments needed. Highly recommended!
How are you handling the Throttle Detent Cable up at the Throttle Shaft on the Injector Pump?
George D. Paxinos

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