81 torque converter will not unlock
Thread Starter
Burning Brakes
Joined: Oct 2004
Posts: 801
Likes: 17
From: Middletown Delaware
81 torque converter will not unlock
Torque converter will not unlock car bogs and stalls at low speeds. All stock and trans is rebuilt. trans shop says its in the car. I checked the brake switch and it is working. Any ideas.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
Either voltage is contstantly being supplied to the Lock-up function of the torque converter, or the unit has sustained mechanical damage from not being used properly (via a lockup controller). That L/U clutch was never meant to pass significant torque through the transmission. The 12vdc signal to engage that clutch MUST be dropped when throttle is increased in upper gear ranges. If not, it will eventually fail. Pull the L/U power connector out of the transmission, then drive to see if it is still engaged. If it is, take the car to the transmission repair shop.
Heel & Toe
Joined: Jun 2003
Posts: 19
Likes: 2
From: Sharpsburg GA
I found this link regarding TCC function and diagnosis. I quickly read through it and it appears to have some very good and quick checks.
https://www.thoughtco.com/diagnosing...roblems-262653
Hope it helps.
https://www.thoughtco.com/diagnosing...roblems-262653
Hope it helps.
Last edited by MI81; Mar 26, 2019 at 07:58 PM.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
Could be a problem within the ECU... or, it could be something amiss with a signal coming in to the ECU. I might suggest that you eliminate the possibility of bad electrical ground or 'dirty' connections by removing all such connectors and terminals, cleaning them, then replacing and trying it again. (Easy fixes are always better!)
Thread Starter
Burning Brakes
Joined: Oct 2004
Posts: 801
Likes: 17
From: Middletown Delaware
ok i have removed all the brake switch plugs 3 each and the egr/tcc relay plugs and I still have 12v at the trans plug pin A. Where is the TCC relay located I have the two relays disconnected from the back of the pass side valve cover but it appears I am missing one that should have a purple wire coming from brake switch.
Last edited by Dave Witman; Mar 27, 2019 at 12:14 PM.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
I still have the belief that the ECU makes the decisions about L/U being On or Off. Does the power from the brake switch go directly to the L/U connector at the trans, or does it get fed to the brake lights and the ECU? IMO, the problem could be with a relay (driven by the ECU), or by an errant ECU signal to that relay.
Pro
Joined: Jun 2016
Posts: 567
Likes: 82
From: Auckland
ok i have removed all the brake switch plugs 3 each and the egr/tcc relay plugs and I still have 12v at the trans plug pin A. Where is the TCC relay located I have the two relays disconnected from the back of the pass side valve cover but it appears I am missing one that should have a purple wire coming from brake switch.
The TCC relay is on the drivers side. You should have a bracket with two relays and the vacuum sensor mounted to it.
This Relay is controlled in two ways: The purple wire from the brake switch switches +12V to the relay, while the ECU switches the ground.
Relay connections are A - Ground
B - Switch ground via ECU (coil-)
C - Switched 12V via brake switch (coil+)
E - Switched ground to EGR/TCC solenoids.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Drifting
Joined: Jul 1999
Posts: 1,542
Likes: 43
From: Plano TX
How important is having the lockup to you? My 80 doesn't have an ECU but still has lockup via brake and vacuum switches. I ran into issues with the port in the solenoid in the trans clogging up. I finally pulled the solenoid from the valve body so lockup was disabled and never looked back.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
The problem with eliminating the L/U function is that the transmission is going to overheat. With L/U engaged, there is little work done by the converter...hence, little heat build up. But, the converter is constantly slipping (ie, working) and generating more heat than the [transmission] cooling system is capable of providing. If you do this, you need to add a trans cooler in the system. It would be easier to fix the L/U problem.