Torque converter unlocking on slight grades

[pasadena_commut]

I noticed the other day that the torque converter in my P5 was unlocked when going up a slight grade, even though the car was moving at a steady 40mph, which is well above the lock speed. Once the road flattened out it locked again. (This is very easy to see by watching the tachometer.) The grade starts near a stoplight, so I figured the car had never reached a high enough speed before the grade, and just stayed unlocked the whole time. Today there wasn't much traffic so I gunned it at that light and had the car up to a steady 40mph well before the grade, and the TC locked. However, without changing pedal pressure, and with only about a 1 or 2 mph loss in speed having taken place, the TC unlocked again shortly after starting up the grade.

I can see why the car would unlock the TC on a steep grade, or if the computer detected the motor bogging down a bit on a shallower grade, but what is the point of the TC unlocking if the car is maintaining speed and not bogging down?

 

[MTV]

Bring it to a tranny shop soon, you don't want the TC shooting metal into the tranny

 

[kboutsider]

Do the automatic P5's have a tcc solenoid? I know when I used to own automatic cavy/sunfires this used to be an issue with them and it was kind of similar.

 

[flash75]

What you describe appears to be normal. You did say the car lost 1-2 mph, that would cause the computer to sense the engine is bogging and unlock the torque converter. Keep in mind the circuit has to be sensitive enough to maintain a constant speed when using cruise control. I don't think you have a problem.

Clifton