I took another listen with the stethoscope. All of the belt driven accesories are relatively quiet running with the exception of the air pump. However, the noise definitely sounds as if it coming from the rear of the engine compartment. Also, the noise is definitely loudest on the transmission dipstick.

The reason I believed the transmission pump was the failing part was because it does "whir" in park. Does the pump not spin when the transmission is not engaged into a gear? Would belt driven accesories change the sound when shifting from park to reverse (more than would be appropriate with the rpm change)?

As a diagnostic step, can anyone advise as to the wisdom of running the car with the polybelt removed?

How would one check if the Bendix gear is not disengaging?

__________________
Kyle Fitzpatrick
Materials Engineer

1969 300SEL 6.3
1992 300E
1994 E320 Touring