torque converter lock up

Hey all,
i have a 86k5, originally had a 305 but i swapped it out for a 400sb years ago, when i did that i got rid of all the emissions stuff and put in a new distributor and by passed the ecm, the 700r4 tranny had the torque converter lock up and i left the pressure switch thats by the brake booster hooked up and i believe it has manifold vacuum running to it. My question for all of you knowledgeable square bodyers out there is, does my tcc still work without the ecm, i dont have a tach and cant really tell by how it feels when im driving

mjck5 said:

Hey all,
i have a 86k5, originally had a 305 but i swapped it out for a 400sb years ago, when i did that i got rid of all the emissions stuff and put in a new distributor and by passed the ecm, the 700r4 tranny had the torque converter lock up and i left the pressure switch thats by the brake booster hooked up and i believe it has manifold vacuum running to it. My question for all of you knowledgeable square bodyers out there is, does my tcc still work without the ecm, i dont have a tach and cant really tell by how it feels when im driving

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I don't think they were ecm controlled till at least 88.

The easiest way to tell if lockup is working is get up to highway speed, past 45-50mph, when you think it's in lockup, and very lightly step on the brake pedal while keeping on the gas. The converter should unlock and rpm should change slightly, should be able to feel/hear it

There is three wires going to the TCC lockup in the 700r4. Yellow goes to an egr bleed valve. You can bypass that, most people just cut it when they bypass the spark control. Green is a test circuit. You may have a green wire by the fuse box with an orange end. If you give it 12v in 4th gear the TCC should lock up. This will let you know if the trans is working/not working or if it is a wiring issue. The blue wire does the work. It leaves the fuse box as a brown wire with 12v ignition power, then hits the brake switch and provides 12v out of the blue wire when the brake peddle is up then onto to the vacuum switch near the brake booster, then to the trans. There is also a blue with a black stripe wire out of the vacuum switch. This goes to the 4x4 circuit to bypass the TCC lockup in 4 wheel drive.

Test it at 45-55mph as stated above. You really don’t even need a tach, it is obvious when the rpm’s jump by 500. If nothing happens, start with the brake switch. They go bad often. Look for 12v on the brown wire at the fuse box and the switch, then make sure the blue wire has 12v when the peddle is up and so-on down the circuit until you get to the transmission connector.

All 700r4s can be run with no ecm and lockup can be made to work. Post a wiring diaghram for the year and vehicle the transmission came from and I can tell you how to wire it. Some required a ground and a hot lead Some the tcc solenoid is grounded in the transmission. If the tcc solenoid doesn't require an external ground then run 12v through a normally closed brake switch through the firewall vacuum switch,to terminal A on the transmission.
Edit, Someone else's was typing while I was and seems they know exactly which lockup solenoid you have so have a great night.
Edit. See the schematic for this car. I'd run 12v through a vaccum switch and a brake switch to terminal #A. I'd jumper terminal #D to terminal #B the 4th gear switch grounds internally. So power would go through A through the lockup solenoid out D through B and ground with the 4th gear switch.

I have an 86 k10 with 700r4. I kept a tvs and went from manifold vacuum to tvs to tcc delay valve to tcc switch. My lock up works. Obviously all the parts still have to work and you have to have sufficient vacuum. You can buy aftermarket lock up control kits.

thanks everyone for all the responses, pretty sure my tcc is hooked up correctly i think i just need to get a tach so i can see it change rpms for myself to be sure.
i was doubting myself after a self proclaimed square body chevy master mechanic swore that without the ecm and all the emissions hooked up correctly that the tcc would not function. but now i see the lock up is a stand alone system regardless if the ecm and emissions are hooked up
thanks everyone

mjck5 said:

thanks everyone for all the responses, pretty sure my tcc is hooked up correctly i think i just need to get a tach so i can see it change rpms for myself to be sure.
i was doubting myself after a self proclaimed square body chevy master mechanic swore that without the ecm and all the emissions hooked up correctly that the tcc would not function. but now i see the lock up is a stand alone system regardless if the ecm and emissions are hooked up
thanks everyone

Click to expand...

I doubt you have an ecm, at most you have an esc that is most likely not hooked up.

jh86 said:

I doubt you have an ecm, at most you have an esc that is most likely not hooked up.

Click to expand...

You are probably right. To the best of my knowledge only California emissions squarebodys had an ecm in 86.

hey everyone, more tcc lock up questions i have been trying to get my tcc lock up working as it should, i have a 86 k5, i replaced the tranny years ago with a rebuilt one out of a 88,apparently they control the lock up differently because my 86 doesn't have an ecm and the 88 does. power runs thru the brake switch and the pressure switch mounted on the firewall and then down to the tranny, i recently replaced the flex plate and torque converter, i thought there might be an issue with my torque converter and that was why my lock up was not working, turns out when i dropped the pan i found out the wiring harness was never plugged in inside the tranny, after i replaced the flex plate and torque converter it would blow the fuse as soon as it went into od, it thought maybe i had an issue with the solenoid so i replaced the solenoid and the wiring harness inside the tranny and the plug, still blew fuse, so i did some digging and realized they are wired differently between 86 and 88, i used the attached wiring diagram to re-wire it going to the tranny. B is not used, A takes 12volt straight to the solenoid, and D is grounded, so now the lock up definitely works but it is locking up in all gears, if i disconnect D then i get no lock up in any gear at any speed, looking at the diagram it shows D as a manual lock up for 2, 3 and 4th gears and disconnected it should only lock up in 4th, i used the stock pressure switches that were in the tranny, the only difference i can think of is the diagram shows 2 terminals on the 4th gear switch and the stock one only has on terminal, i assumed it was grounded thru the casing to close the switch, i did not wire in a on off switch or any of the leds shown in the diagram, i figured unhooking D would be the same and im not really looking to have lock up in all gears just in od, am i missing something or do i need to replace the 4th gear switch with one with 2 terminals? any help/advice would be appreciated,

I went round and round with this very same issue on my 1987 V10 when I first got it. From the look of the remains of the TCC plug dangling next to the trans and the plug socket filled with 40 years worth of dirt the original owner unplugged TCC the day he drove the truck off the lot. Might explain the receipt for a trans rebuild at 80k miles.

Anyway, I got lockup working the way the factory intended and hated it. In 1987 they had it set up with multiple pressure switches and also ECM input and had it so it locked up as soon as you shifted to 3rd, unlocked momentarily for the 3-4 upshift, then locked again instantly in 4th. Since all my around town driving is between 35-45mph that just means I was constantly upshifting and downshifting and locking up and lugging the motor and unlocking and locking again and it was incredibly annoying.

Anyway, after pulling the pan and messing around and trying to figure out what to unplug and not unplug and which pressure switches to remove and which to keep and all that I broke down and ordered the Bowler Transmission kit and threw that in along with a pan with a drain plug since I was already there. Now I’ve got lockup in 4th only, with a switch on the dash to turn it on or off if I choose, plus it’s got a module that provides a 10 second delay before lockup occurs. So around town I leave lockup switched off, but if I’m on the feeder road about to get on the freeway I throw the switch and it’s locking up right about the time I’m up to 55mph or above and it’s perfect. Brake still disengages it, cruise control works with it, simple as can be. Looks like it’s on backorder right now but I highly recommend getting this. It totally solved my problems with lockup and this kit works whether you’ve got a ECM like I do or not. If you do it takes the ECM completely out of the equation.