I have a 1996 pontiac grand am 2.4l with a 4t60 trans that will not keep the tcc engaged.I have already replaced the valve body,computer,and torque converter itself.Is it true that these transmissions have an accumulator for the converter?

There are a couple things with the PCM that will not allow TCC lockup.

If the engine has not warmed up to a certain temp.
If the transmission has not warmed up
If you have a faulty brake switch, it will prevent TCC lockup.

Have you scanned for any codes?

Also, Inconsistant timing will disable lock up. (Knock)

Was the TTC solenoid replaced with the valve body?

Mike and Mike, could an incorrectly adjusted TV or whichever adjustable cable is on the 60 cause any lockup problems?

I know so litle about the 60....

I'm assuming this is a 4t60e since it'* a 96 so there would be no TV cable. Do you mean the gear selecting cable?

Nope, I meant the non-existant cable. It'* not that often that I work on one and therefore I was hunting for other ideas that didn't exist.

Bill your confusing me now???

Anyway, a bad TPS can prevent TCC lockup too, but your engine would be hesitant at the same time. Ummm, possible a bad IAT sensor too??

the converter is engaging but will only stayed engaged for a few seconds making the engine surge between 2000-2200 rpms at highway speeds.I have replaced the knock sensor because when I was removing the trans. I broke it accidentally.I also used the entire valve body out of a salvage vehicle(solenoids included).It doesnt have any codes!It seems to me that the computer itself is causing the surge since I tapped into the TCC and TCC PWM solenoids and the computer grounds these at the time I feel the surge.But the computer itself was replaced out of a salvage vehicle as well.

Are you able to monitor the line voltage on the TCC engage circuit while driving? I'd like to see if its the PCM making the TCC unlock/lockup.

Is have not tried to hook up any fluid pressure gauges to the transmission yet.Where is the line pressure tap on this transmission?Voltage to the TCC solenoids stays at battery voltage the entire time the engine is running.