I know this subject has been beat to death but I have a specific question with regard to quality of shifts.

I have a '91 300E with 62K on it. From the day I bought it, the transmission shifts were firm but more than acceptable with the A/C compressor OFF. If I simply turn the compressor ON, the shifts become overly hard. I've had to replace the Flex disk recently which was probably caused by the hard shifts.

Can someone rationalize why the A/C compressor would cause this problem and could an experienced technician solve the problem?