4L60E Convertor Lockup Issue
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Teching In
Joined: Apr 2022
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4L60E Convertor Lockup Issue Just got done doing a LS1 swap with a 4L60E trans in a 1966 Impala SS. The transmission up shifts and down shifts great. The issue I am having is when the trans heats up the convertor stays locked up and the car surges when I am at a stop. It does it in reverse as well as all the forward gears. Hooked the scanner up to it and there are no codes. The transmission is not running hot. Any ideas would be really helpful.
TECH Fanatic
Joined: Jan 2018
Posts: 1,250
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From: Dade City, Fl.
Brake Switch Signal - For automatics with lock up converter, the PCM needs signal when brake pedal is pressed. However, the signal needed is opposite how you're brake lights work. The PCM wants 12v+ constant on this wire when brake IS NOT pressed, and OPEN Circuit when the brake IS pressed. If you vehicle was equipped with a lockup trans to begin with, you probably already have the proper normally closed switch mounted by your brake light switch. If you do not, you can use a relay to perform the same thing. On most relays, there are 5 terminals, 2 of them turn the relay ON when provided ground/power. There are then a normally open leg and a normally closed leg on the relay and a supply. By feeding 12v+ on the supply leg, and hooking the Brake Switch Signal wire to the normally closed leg, you will now have the correct signal for the PCM. When the brake is pressed, 12v+ flows to brake lights, tap into this wire, and run it to the relay to turn the relay on. This will cause the normally closed leg to become open, thus turning OFF the 12v+ signal to the PCM. When you release the brake pedal, the relay will turn OFF, and then feed 12v+ to the PCM.
