The piece in question should be the modulator. It's on the driver's side of the transmission about half way back. It senses engine load through a vacuum line to control the shift points. There are other inputs from the throttle cable and kick-down switch.
If the car is a diesel, there is another vacuum related piece on the injection pump that sends a signal to the modulator. Either one is important to proper
operation of the transmission. What is the car doing?
ASE Master Tech
Mercedes Tech 21 Years
68 SAAB 96 Ice Racer
69 300SEL 6.3
70 300SEL 3.5