How does lockup converter activate?

[Walts_restoration]

On my 86 k5, im swapping the tired old 86 305 for a 75 350 nonemissions, witch the PO had already started for me, but im gonna try to keep cruise, and the 700r4 for now (till she blows up) and the lockup converter. Ive still got the 86 quadrajet, but im gonna use the quadrajet off the 75 motor.

My question is, how does the lockup converter, well lock? what switches do i need to keep? what sends the signal? it had already been modded before i got it, PO took off most of the computer stuff. thanks guys.

[Thumpin455]

There is a four prong connector in the drivers side of the case. One of the wires activates the solenoid that locks the converter. It sends pressure to the clutch through the input shaft, the clutch itself locks to the front part of the converter housing, effectively locking the engine to the input shaft with no slippage.

You can wire it with a toggle switch, but when you stop you need to unlock it or you will tear things up. B&M and I think TCI sell kits that will lock and unlock the clutch for you, I have the B&M kit on my GTO with a 2004R, works ok. It only needs 12v to lock, no computer needed prior to 1993 with any of the 700R4/4L60 transmissions, only the 4L60E needs a computer. I can check the manual if you need to know what pin needs power to lock the converter. FYI if you dont lock it and continue to drive, somewhere around 1000-5000 miles later the trans will die from heat buildup. Ask how I know..

One thing you need to be aware of with the Qjets is the geometry for the TV cable. The 75 Qjet might not have the right arm on the throttle shaft for the TV cable, but the 86 Qjet does. Measure the distance from the shaft centerline to the pin the TV connected to on the 86 carb, sometimes they are different or not even there.

If the TV isnt right you will burn the transmission up in no time. It acts like the vacuum modulator did in that it is part of the system that controls line pressure, and if it is too high it will blow the seals out and or break the pump, if its too low it will burn clutches. One notch on the cable makes a big difference in line pressure and shift points. Really the best way to set the TV is with a line pressure gauge, but unless you do them often its tough to justify the $100+ price of the kit. Of course if it isnt right, it will die in less than 20 miles, and the $100 will look cheap compared to a rebuild.

Anyway the 86 Qjet shouldnt be the computer assisted one, or at least its possible it isnt. The 87 C20 I got my 454 from didnt have the E carb on it. If yours is a normal one with no electrical connections near the fuel inlet, then use the 86 carb. That would simplify things with the TV, cruise, and throttle linkage.

[87Bob]

Originally Posted by Thumpin455

There is a four prong connector in the drivers side of the case. One of the wires activates the solenoid that locks the converter. It sends pressure to the clutch through the input shaft, the clutch itself locks to the front part of the converter housing, effectively locking the engine to the input shaft with no slippage.

You can wire it with a toggle switch, but when you stop you need to unlock it or you will tear things up. B&M and I think TCI sell kits that will lock and unlock the clutch for you, I have the B&M kit on my GTO with a 2004R, works ok. It only needs 12v to lock, no computer needed prior to 1993 with any of the 700R4/4L60 transmissions, only the 4L60E needs a computer. I can check the manual if you need to know what pin needs power to lock the converter. FYI if you dont lock it and continue to drive, somewhere around 1000-5000 miles later the trans will die from heat buildup. Ask how I know..

One thing you need to be aware of with the Qjets is the geometry for the TV cable. The 75 Qjet might not have the right arm on the throttle shaft for the TV cable, but the 86 Qjet does. Measure the distance from the shaft centerline to the pin the TV connected to on the 86 carb, sometimes they are different or not even there.

If the TV isnt right you will burn the transmission up in no time. It acts like the vacuum modulator did in that it is part of the system that controls line pressure, and if it is too high it will blow the seals out and or break the pump, if its too low it will burn clutches. One notch on the cable makes a big difference in line pressure and shift points. Really the best way to set the TV is with a line pressure gauge, but unless you do them often its tough to justify the $100+ price of the kit. Of course if it isnt right, it will die in less than 20 miles, and the $100 will look cheap compared to a rebuild.

Anyway the 86 Qjet shouldnt be the computer assisted one, or at least its possible it isnt. The 87 C20 I got my 454 from didnt have the E carb on it. If yours is a normal one with no electrical connections near the fuel inlet, then use the 86 carb. That would simplify things with the TV, cruise, and throttle linkage.

Someone is making a kit that does away TV cable adujustment concern. You still have it but if it is not adjusted correctly it wont tear up the tranny.

[Walts_restoration]

its got the electrical connoectors like my moms 84 monte carlo for the computer controlled carb, it was probably the light duty 305 4v

[gchemist]

http://www.73-87.com/7387garage/drivetrain/lockup.htm

[LEEVON]

Originally Posted by gchemist

http://www.73-87.com/7387garage/drivetrain/lockup.htm

That article is great, but I don't see the need to switch to the TH400 single pin connector. I got the vacuum switch and 4-pin 700R4 plug free from the junkyard, there were a bunch of them. Be sure to get the little blue booster too. Also get a brake cancel switch which are plentiful at the junkyard. My truck had one already for the cruise control, yours might too if it has cruise and they have a second set of contacts just for this purpose.

Wire 12v switched with a 10A fuse to the brake switch, then vacuum, then the tranny. Both switches are normally closed, the idea is to break the 12v supply under heavy accelleration or braking. Your tranny is most likely wired for the factory lock-up function. I had '83 and '91 trannys and although both were a little different internally they were ready to go. If you're like me and you don't want to mess with the factory set-up internally then just plug and go.

ps - the vacuum switch is mounted on the brake booster, it could still be there.

[Walts_restoration]

with all this stuff, makes me want to switch out to a th350 lol.