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700R4 transmission in a HMMWV

Subaugusta710

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Hi Guys, I’m swapping 700r4 for TH400 and getting ready to order the torque converter lock-up circuit. Do I need the dual brake switch to drop out the lock-up? If so, what switch is recommended? Also… could use some advice on how to configure the TV cable and shift linkage. I’m in a 1986 M998 that I’m converting from stock. Thanks!
 

Mogman

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Hi Guys, I’m swapping 700r4 for TH400 and getting ready to order the torque converter lock-up circuit. Do I need the dual brake switch to drop out the lock-up? If so, what switch is recommended? Also… could use some advice on how to configure the TV cable and shift linkage. I’m in a 1986 M998 that I’m converting from stock. Thanks!
Have the transmission built with a 4th gear pressure switch in the valve body, then just wire up the torque converter solenoid to that switch, it will only go into lockup in 4th gear, nothing else needs to be switched, this can also be done after the transmission is built all you have to do is tap the 4th gear servo cover and put a switch in it.
EDIT, the 4th gear servo cover is the round thing on the right side of the transmission.
servo.jpg
Of course you want to remove the cover, there is just a wire ring holding it in, you would have to depress it a little to get the ring out, there is a spring against that cover.
 
Last edited:

Milcommoguy

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Have the transmission built with a 4th gear pressure switch in the valve body, then just wire up the torque converter solenoid to that switch, it will only go into lockup in 4th gear, nothing else needs to be switched, this can also be done after the transmission is built all you have to do is tap the 4th gear servo cover and put a switch in it.
EDIT, the 4th gear servo cover is the round thing on the right side of the transmission.
View attachment 880488


🤔🤔 Not a whizz at transmissions... BUT how are the tranny swapper (that reads wrong) dealing with the TC lock-up solenoid / coil voltage requirements?

Are they hitting it with 12 Volts (tapped battery) or slamming it with 24 Volts. Like is there a 24 Volt coil or who cares or dropping resistor / proper wattage?

Just 🤔 at the keyboard and bored.

Now I gota wizz, LOL, CAMO
 

Subaugusta710

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I believe I asked them to include the solenoid. It has the 4 pin connector. So I should be good to go once I install the lockup circuit? I already wired a 24v to 12v converter in the truck. 15 amp fused circuit. 1630CD50-D7B8-4940-B65E-AECD6B6FEB72.jpeg
 

Mogman

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All transmissions (that we would be talking about) are 12V even the 4L80 they put in the HMMWV,
They should have given you a schematic, all you have to do is wire 12V through the pressure switch to the lockup solenoid, unless they did that for you inside the transmission, again they should have given you that information.
 

Mogman

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The 700R4 I was building before I decided to go 6L80 had pressure switches on 3rd and 4th gear so it would lock up in 3rd and 4th
 

Subaugusta710

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Update: the 700R4 is installed but not yet complete. The shop I used did most of the work. I need to finish shifter linkage, and run 12v signal to trans for brake switch. I did drive it about 50 miles on the interstate manually shifting. My recorded top speed was 75mph. It will run 70mph but struggles on inclines. I'll have more info when the small bits sorted. I do not have a tachometer.
I'm wrapping up my 700r4 conversion and am struggling to come up with an easy adapter for the shifter linkage. Do you happen to have any photos of your linkage that you built? Would appreciate your advice. I really don't want to pay $$$ for the 4 speed shifter... at least not right now. Thanks
 
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