My 1993 500 E suddenly developed a loud low pitched whining or high pitched growling noise in the transmission that is louder and higher pitched with increased engine speed.

The mechanic hears it above the forward portion of the pan, although I maybe too optimistically seem to be hearing it in the area of the torque converter. The filter was found to be unusually heavy. Any ideas as to cause or solution before it is pulled out?

Secondly, if a rebuild is required, is there any advice about the factory rebuilts, or alternatives?