700R4 transmission in a HMMWV

[Mogman]

I have this question too.
If the input gear (NP21 is changed to a 27 spline then the stock NP241/700R4 transmission/transfer case adapter and original 27 spline 700R4 output shaft should work yes?
I have not been able to find a 32 spline output shaft but only the $500 Advanced Adapters kit for direct adaptation to the 32 spline NP218,
27 spline NP208 input gears are plentiful (same gear as the NP21

 

[87m998]

Best bet call advance adapters and they can explain all. I only had the short shaft, plate 4 bolts and o ring when I put mine together. The adapter plate can be mounted to the 700r4 two ways but only fits up to the 218 one way. With this set up no driveshaft mods are required. Hope that helps a little.

 

[jdknech]

I went with a 700r4 in my m998 a couple years ago. I used the kit from advanced adapters to mate it to the factory np242 transfer case, and had a local (trusted) trans shop build it to diesel specs. Hardest part was making the TV cable bracket. I would not recommend towing with it, but it was definitely worth the effort

 

[Lazboytt]

I went with a 700r4 in my m998 a couple years ago. I used the kit from advanced adapters to mate it to the factory np242 transfer case, and had a local (trusted) trans shop build it to diesel specs. Hardest part was making the TV cable bracket. I would not recommend towing with it, but it was definitely worth the effort

Do you have the part number for the adapter kit? Besides that adapter and having the trans built for a diesel truck and the TV cable bracket is there anything else that needs to be done?


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[jdknech]

Do you have the part number for the adapter kit? Besides that adapter and having the trans built for a diesel truck and the TV cable bracket is there anything else that needs to be done?


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I don’t have the part number handy, it wasn’t hard to find on there website though. I did have to change out the flexplate, but everything else bolted right up.. even the trans crossmember didn’t have to be modified, and the driveshafts bolted right back in place

 

[jdknech]

Do you have the part number for the adapter kit? Besides that adapter and having the trans built for a diesel truck and the TV cable bracket is there anything else that needs to be done?


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50-6901 : GM 700R4 to GM NP208 Adapter Kit (replacing TH400) | Advance Adapters

Advance Adapter The GM 700R4 main shaft kit is used when replacing a TH400 in model years 1985-91. Once installed into the 700R4, the output side of the 700R4 looks identical to a 4WD TH400 that is being replaced. The adapter kit includes a new output...

www.advanceadapters.com

 

[Lazboytt]

Anyone know if there is a tv cable bracket available that would work or best way to make one?

I’m a novice with this so looking for any info.
The link to the kit is great information and should be stickied


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[Lazboytt]

Do you need to do any wiring or switches to make the transmission work? I was looking at the following transmission by monster transmissions unless anyone has a different recommendation

700r4 Transmission Super Duty 4WD, 700r4 transmission, rebuilt 700r4 transmissions, gm 700r4 transmission, performance 700r4, 700r4 rebuild

www.monstertransmission.com

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[suzukovich]

Not mistaken these are the guys who came up with the conversion kit for the HMMWV. I haven't done it yet but do know some who have and love it. You will have to get a new shifter. Transmission also comes with a park brake. Call them. Hopefully some will chim in who have done the conversion.

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[USCDOC]

I’m in the middle of this 3L80 to 700R4 conversion. I used Monster transmission bc I thought they were legit. DO NOT USE THEM. I figured by using someone like them that’s been on TV and all that I would be getting a very squared away product. It turns out that I had to replace the output shaft because the wrong one was put in, that was easy, but multiple internal parts were USED and worn out requiring replacement. Only $500 to fix it. The reason why I paid for it is because they will not return my phone calls to honor the warranty for a tranny I haven’t even used yet. They also said they were installing a billet input shaft which was a complete lie. I had to reverse the $777 charge on my credit card. Terrible company. Terrible customer service. I did run into having to change the flex plate and the transmission crossmember does not lineup. The transmission support mount that they sent does not work either because it is not tall enough. I’ve seen that many people have said it does and it certainly does not. Going to have to modify this one(move it forward about 2 inches. That’s either going to require drilling new holes in the frame for the crossmember, or welding on an adapter plate. I have the advanced adapters kit and all lines up well otherwise. Any advice on crossmember modification? Looks like I will have to drill holes in the foot wells of the rear passenger area in order to get the bolts that go through the frame that hold the crossmember mount out. Tips or pointers? Tia

 

[87m998]

I’m in the middle of this 3L80 to 700R4 View attachment 787745conversion. I used Monster transmission bc I thought they were legit. DO NOT USE THEM. I figured by using someone like them that’s been on TV and all that I would be getting a very squared away product. It turns out that I had to replace the output shaft because the wrong one was put in, that was easy, but multiple internal parts were USED and worn out requiring replacement. Only $500 to fix it. The reason why I paid for it is because they will not return my phone calls to honor the warranty for a tranny I haven’t even used yet. They also said they were installing a billet input shaft which was a complete lie. I had to reverse the $777 charge on my credit card. Terrible company. Terrible customer service. I did run into having to change the flex plate and the transmission crossmember does not lineup. The transmission support mount that they sent does not work either because it is not tall enough. I’ve seen that many people have said it does and it certainly does not. Going to have to modify this one(move it forward about 2 inches. That’s either going to require drilling new holes in the frame for the crossmember, or welding on an adapter plate. I have the advanced adapters kit and all lines up well otherwise. Any advice on crossmember modification? Looks like I will have to drill holes in the foot wells of the rear passenger area in order to get the bolts that go through the frame that hold the crossmember mount out. Tips or pointers? Tia

Knew there was something wrong with your pic LOL, the cross member bolts to the xfer case not the trans. All will be well when you mount the xfer case.
Cheers

 

[Awol]

Monster Transmission is pretty awful. They built their company on paid advertising and sponsoring tv builds.

Not the first time I've heard of them using used and worn out parts in a "rebuilt" transmission.

 

[USCDOC]

Wow thanks! I’ll take another look!

 

[USCDOC]

Omg I feel so dumb!!! Thanks so much. I was confused bc they sent a transmission mount with the transmission that is not necessary! Ha! Happy I don’t have to deal with that. Do the 2 extra wires coming off the 4L80 shifter hook directly to the 2 wires out of the transmission? Does it matter which?

 

[87m998]

The wires coming from the shifter connect to the three wires you disconnected from the old shifter. Neutral saftie switch and such. I only had one connector coming off my 700r4 which I hooked to a 12v source from the gen for the lockup.

 

[USCDOC]

The wires coming from the shifter connect to the three wires you disconnected from the old shifter. Neutral saftie switch and such. I only had one connector coming off my 700r4 which I hooked to a 12v source from the gen for the lockup.

Oh cool. I guess you used the old shifter? I say that Bc there are 5 wires off the new HMMWV shifter that came with the 4L80E transmission in the M998. 3 are the same. Wondered if it was reverse lights. That would be awesome bc I have a separate switch for that

 

[87m998]

My new shifter only has three wires for ind lights and saftie switch. Would not know what the other two are for.

 

[USCDOC]

Do you need to do any wiring or switches to make the transmission work? I was looking at the following transmission by monster transmissions unless anyone has a different recommendation

700r4 Transmission Super Duty 4WD, 700r4 transmission, rebuilt 700r4 transmissions, gm 700r4 transmission, performance 700r4, 700r4 rebuild

www.monstertransmission.com

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Do not use Monster. They are TERRIBLE!!!!

 

[USCDOC]

50-6901 : GM 700R4 to GM NP208 Adapter Kit (replacing TH400) | Advance Adapters

Advance Adapter The GM 700R4 main shaft kit is used when replacing a TH400 in model years 1985-91. Once installed into the 700R4, the output side of the 700R4 looks identical to a 4WD TH400 that is being replaced. The adapter kit includes a new output...

www.advanceadapters.com

Advanced adapters are AMAZING and very helpful. Call them to order so you get the exact kit. I am having a hard time finding the TV cable bracket(Monster transmission are idiots and sent the wrong one and will not call me back). I took it in to a transmission shop to do that part b/c it is the most important part of the swap. Otherwise, the swap kit is really not much of a swap kit for the HMMWV... they designed it for 2WD cars w/normal carbs. Dipstick is a PITA too. I modified the one they sent, and it will require I pull dog house off to check it b/c its too short. The TV bracket they sent is totally wrong and for a carb like a holley. Monster is TERRIBLE. I would not use them. I would use anyone else, and make sure you get the TV bracket for your engine throttle included and a better dipstick. The flex plate had to be replaced and torque converter was 3 bolt pattern. It was a simple swap, but so many BS steps b/c it wasn't straight forward like they all claim.

 

[87m998]

You can adapt your old bracket with a file so that the square cable end fits in the old round hole. Just hand file it or use a dremel. It can be done just give it a look.