4T60E problem.

[steveo358]

Hi Im new to this site, and was looking for help. I have a pontiac bonneville 4T60E. When cruising , all of a sudden chime comes on, and car seems like it comes out of drive. Speedometer goes up and returns.car seems to do fine after. This seems like a electrical prob in tranny to me, but I dont know what. I am getting a P0740 code from it. Any help would be greatly appreciated. I changed filter and fluid, and everything looked normal in the pan.
Thanks for you guys time,
Steve

[prophiseer]

someone correct me if I'm wrong, but I think the p0740 code is for a Torque Converter Clutch circuit malfunction. What's going on is the PCM is losing control of the Torque Converter Clutch (TCC), so without the voltage from the PCM to the TCC solenoid, the TCC will disengage - hence the feel that the tranny is falling outta gear, an the speedo going up, RPM's are more than likely jumpin up with it, also. More than likely, it's just the TCC solenoid starting to go bad, or a loose or corroded connection at the tranny casing (slight possibility it's a poor connection internal to the tranny). Worst case scenario the TCC itself is going bad.

It would require more diagnosis, but that's the direction you should go. I'm about 98% sure it's a tranny electrical problem, though.

If it defi is the TCC going bad, there's an easy and extremelly cheap fix . . .

[steveo358]

Is the tcc solenoid something that I can access,and or diagnose, or do I need a tranny man to do this? And what may be the "easy and cheap fix"?

[prophiseer]

I can't remember clearly, but I think the TCC solenoid can be accessed from the side of the tranny once you take the valve body cover off. You should prob drain the tranny first. You'll have to look up the exact location of the solenoid, but it should be an easy swap.

The easy fix for a TCC going bad . . . some early to mid '90s T60's had a two wire connector above the main tranny harness that plugs into the case. If you unplug it the TCC can't be engaged and the car will still drive just fine.

But with OBDII, you might have to unhook some wire from the harness to do this; it all depends on the year.