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Torque Converter install help.
Thread Starter
Le Mans Master
Joined: Jul 2016
Posts: 8,433
Likes: 392
From: Oklahoma
Torque Converter install help.
Cliffs: for those that weren’t following;
DUB pulled my newly rebuilt 400 on my 1968 /427 and installed 700r trans (w/o my knowledge). it’s not complete as torque converter not wired in.
There is a red wire @ the trans that I assume needs to run to 12 V, but how does all this hook into brake etc? Do we need some kind of relay?
Shiftworks shifter upgrade was installed but can’t figure out the rest of the torque converter install.
Clueless here.
Any help with diagrams etc would be helpful.
DUB pulled my newly rebuilt 400 on my 1968 /427 and installed 700r trans (w/o my knowledge). it’s not complete as torque converter not wired in.
There is a red wire @ the trans that I assume needs to run to 12 V, but how does all this hook into brake etc? Do we need some kind of relay?
Shiftworks shifter upgrade was installed but can’t figure out the rest of the torque converter install.
Clueless here.
Any help with diagrams etc would be helpful.
Last edited by c1nicole; Jun 19, 2025 at 08:26 AM.
2026 Loser of the Year
Joined: Sep 2013
Posts: 36,607
Likes: 7,053
From: New Or-leens Loo-z-anna
DID DUB GIVE YOU YOUR REBUILT TH400 TO YOU?
THE 700R4 IS A FUEL SAVER ON THE HIGHWAY, THOUGH.
There is a guy on YouTube who wires a relay into the brake light power wire on the firewall. This turns off the Lockup when you hit the brakes...which keeps the engine from killing at traffic lights, etc.
The Red wire at the transmission case would connect to one terminal of the relay so the converter lockup has power to it in "4th Gear" when in DRIVE or DRIVE 2 (Lockup is engaged when the valve body 3rd gear pressure switch reaches max pressure)
When the Brake pedal is pressed while the car is in DRIVE, the lockup turns OFF.
One of the pressure switches screwed into the Trans Valve Body has to be changed so the Trans engages the Lockup when the 3rd gear pressure reaches maximum pressure.
I forget what the other pressure switch does or if it is eliminated entirely.
I may be able to find a hand-drawn wiring diagram from 15 years ago tomorrow. P.M. me if I forget
Hopefully someone can fill in the blanks.
The Member in Austrailia documented his entire 700R4 swap. MAYBE other members will remember his thread or supply their own information.
The Re-wiring and pressure switch Mod is not difficult once you have a wiring diagram.
INSTALLING A RELAY ON THE FIREWALL SAVES YOU FROM FIGHTING THE BRAKE SWITCH MOD UNDER THE DASH!
THE 700R4 IS A FUEL SAVER ON THE HIGHWAY, THOUGH.
There is a guy on YouTube who wires a relay into the brake light power wire on the firewall. This turns off the Lockup when you hit the brakes...which keeps the engine from killing at traffic lights, etc.
The Red wire at the transmission case would connect to one terminal of the relay so the converter lockup has power to it in "4th Gear" when in DRIVE or DRIVE 2 (Lockup is engaged when the valve body 3rd gear pressure switch reaches max pressure)
When the Brake pedal is pressed while the car is in DRIVE, the lockup turns OFF.
One of the pressure switches screwed into the Trans Valve Body has to be changed so the Trans engages the Lockup when the 3rd gear pressure reaches maximum pressure.
I forget what the other pressure switch does or if it is eliminated entirely.
I may be able to find a hand-drawn wiring diagram from 15 years ago tomorrow. P.M. me if I forget
Hopefully someone can fill in the blanks.
The Member in Austrailia documented his entire 700R4 swap. MAYBE other members will remember his thread or supply their own information.
The Re-wiring and pressure switch Mod is not difficult once you have a wiring diagram.
INSTALLING A RELAY ON THE FIREWALL SAVES YOU FROM FIGHTING THE BRAKE SWITCH MOD UNDER THE DASH!
Last edited by doorgunner; Jun 18, 2025 at 11:14 PM.
Melting Slicks
Joined: Aug 2016
Posts: 2,347
Likes: 1,181
From: CLEVELAND STUCK IN OHIO
2024 C3 of the Year Finalist- Modified
.....You'll really need to know how your trans was rebuilt or modified or not at all BEFORE you guess as to the best way to hook up wireing or if its not needed at all.Its possible the lock up is eliminated,,, or not the proper converter,,, internal switching could be changed,,,, you really need to know what you exactly have first. Then you can correctly proceed.......
Melting Slicks
Joined: May 2021
Posts: 2,281
Likes: 1,325
From: Fleming Island, FL
Personally I wouldn't use a 700r4 or a 350 hydramatic behind a big block.
There's a million torque converter lockup schemes out there including many different schemes that GM use themselves. But the one scheme that stood out to me was when I was flipping through a factory service manual for a light duty truck. In the manual it showed a 700r4 wiring diagram for use behind a diesel. It just used a 4th gear pressure switch straight to 12 volts. No brake switch, no vacuum switch (obviously), no delay module or anything else. So I question the need any other peripheral switching. Also Trans Go has a kit that handles converter lockup completely hydraulically. https://www.summitracing.com/parts/trg-700-lu
However this kit only works the earlier 700r4 valve bodies that have been drilled to accept this valve. It's almost as if GM intended to use hydraulic only converter lock up in the initial stages of planning but decided to go electric.
There's a million torque converter lockup schemes out there including many different schemes that GM use themselves. But the one scheme that stood out to me was when I was flipping through a factory service manual for a light duty truck. In the manual it showed a 700r4 wiring diagram for use behind a diesel. It just used a 4th gear pressure switch straight to 12 volts. No brake switch, no vacuum switch (obviously), no delay module or anything else. So I question the need any other peripheral switching. Also Trans Go has a kit that handles converter lockup completely hydraulically. https://www.summitracing.com/parts/trg-700-lu
However this kit only works the earlier 700r4 valve bodies that have been drilled to accept this valve. It's almost as if GM intended to use hydraulic only converter lock up in the initial stages of planning but decided to go electric.
Thread Starter
Le Mans Master
Joined: Jul 2016
Posts: 8,433
Likes: 392
From: Oklahoma
DID DUB GIVE YOU YOUR REBUILT TH400 TO YOU?
THE 700R4 IS A FUEL SAVER ON THE HIGHWAY, THOUGH.
There is a guy on YouTube who wires a relay into the brake light power wire on the firewall. This turns off the Lockup when you hit the brakes...which keeps the engine from killing at traffic lights, etc.
The Red wire at the transmission case would connect to one terminal of the relay so the converter lockup has power to it in "4th Gear" when in DRIVE or DRIVE 2 (Lockup is engaged when the valve body 3rd gear pressure switch reaches max pressure)
When the Brake pedal is pressed while the car is in DRIVE, the lockup turns OFF.
One of the pressure switches screwed into the Trans Valve Body has to be changed so the Trans engages the Lockup when the 3rd gear pressure reaches maximum pressure.
I forget what the other pressure switch does or if it is eliminated entirely.
I may be able to find a hand-drawn wiring diagram from 15 years ago tomorrow. P.M. me if I forget
Hopefully someone can fill in the blanks.
The Member in Austrailia documented his entire 700R4 swap. MAYBE other members will remember his thread or supply their own information.
The Re-wiring and pressure switch Mod is not difficult once you have a wiring diagram.
INSTALLING A RELAY ON THE FIREWALL SAVES YOU FROM FIGHTING THE BRAKE SWITCH MOD UNDER THE DASH!
THE 700R4 IS A FUEL SAVER ON THE HIGHWAY, THOUGH.
There is a guy on YouTube who wires a relay into the brake light power wire on the firewall. This turns off the Lockup when you hit the brakes...which keeps the engine from killing at traffic lights, etc.
The Red wire at the transmission case would connect to one terminal of the relay so the converter lockup has power to it in "4th Gear" when in DRIVE or DRIVE 2 (Lockup is engaged when the valve body 3rd gear pressure switch reaches max pressure)
When the Brake pedal is pressed while the car is in DRIVE, the lockup turns OFF.
One of the pressure switches screwed into the Trans Valve Body has to be changed so the Trans engages the Lockup when the 3rd gear pressure reaches maximum pressure.
I forget what the other pressure switch does or if it is eliminated entirely.
I may be able to find a hand-drawn wiring diagram from 15 years ago tomorrow. P.M. me if I forget
Hopefully someone can fill in the blanks.
The Member in Austrailia documented his entire 700R4 swap. MAYBE other members will remember his thread or supply their own information.
The Re-wiring and pressure switch Mod is not difficult once you have a wiring diagram.
INSTALLING A RELAY ON THE FIREWALL SAVES YOU FROM FIGHTING THE BRAKE SWITCH MOD UNDER THE DASH!
Thanks for that information.
thisnis the single red wire coming of that white cube. Only wore coming out of the trans so I assume internal ground.
There is also overdrive attached to the carb.
Last edited by c1nicole; Jun 19, 2025 at 08:37 AM.
Thread Starter
Le Mans Master
Joined: Jul 2016
Posts: 8,433
Likes: 392
From: Oklahoma
.....You'll really need to know how your trans was rebuilt or modified or not at all BEFORE you guess as to the best way to hook up wireing or if its not needed at all.Its possible the lock up is eliminated,,, or not the proper converter,,, internal switching could be changed,,,, you really need to know what you exactly have first. Then you can correctly proceed.......
Im still at a complete loss as to why my trans was pulled. I highly suspect he was harvesting parts from my car for other jobs as it was during COVID and you couldn’t get parts. Changes were made to my car that were not needed or approved. He was to only have my car for 18 months for interior install and paint. He had my car for 5 yrs and…. When he died got my car back in many pieces with a long list of unanswered questions as to why he did the things he did. .
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Burning Brakes
Joined: Apr 2020
Posts: 792
Likes: 422
From: Western NY
Pretty sure the second cable hooked to the throttle is for the TV cable which controls line pressure for the shifts. that needs to be adjusted correctly before you drive the car or the trans will be wrecked before you get to the end of your street.
Pat
Pat
Thread Starter
Le Mans Master
Joined: Jul 2016
Posts: 8,433
Likes: 392
From: Oklahoma
.....You'll really need to know how your trans was rebuilt or modified or not at all BEFORE you guess as to the best way to hook up wireing or if its not needed at all.Its possible the lock up is eliminated,,, or not the proper converter,,, internal switching could be changed,,,, you really need to know what you exactly have first. Then you can correctly proceed.......
Thread Starter
Le Mans Master
Joined: Jul 2016
Posts: 8,433
Likes: 392
From: Oklahoma
I believe that has been set. Going to have to have someone way smarter than us to confirm.
Melting Slicks
Joined: Aug 2016
Posts: 2,347
Likes: 1,181
From: CLEVELAND STUCK IN OHIO
2024 C3 of the Year Finalist- Modified
2026 Loser of the Year
Joined: Sep 2013
Posts: 36,607
Likes: 7,053
From: New Or-leens Loo-z-anna
How about removing the trans pan and post some pics of the valve body wiring and the pressure switches?...you guys will notice things/mods that can help rewire the Lockup Converter (if it exists).
No need to disassemble the valve body itself.
ALSO... is there a number or symbol on the torque converter that will provide clues as to whether the T.C. is the LOCKUP VERSION....
or it is a NON-LOCKING CONVERTER?
No need to disassemble the valve body itself.
ALSO... is there a number or symbol on the torque converter that will provide clues as to whether the T.C. is the LOCKUP VERSION....
or it is a NON-LOCKING CONVERTER?
Thread Starter
Le Mans Master
Joined: Jul 2016
Posts: 8,433
Likes: 392
From: Oklahoma
How about removing the trans pan and post some pics of the valve body wiring and the pressure switches?...you guys will notice things/mods that can help rewire the Lockup Converter (if it exists).
No need to disassemble the valve body itself.
ALSO... is there a number or symbol on the torque converter that will provide clues as to whether the T.C. is the LOCKUP VERSION....
or it is a NON-LOCKING CONVERTER?
No need to disassemble the valve body itself.
ALSO... is there a number or symbol on the torque converter that will provide clues as to whether the T.C. is the LOCKUP VERSION....
or it is a NON-LOCKING CONVERTER?
Literally was why I paid someone to do that for me before it went to NC, this girl is not mechanically inclined. 😂