Your complaint is that the transmission shifts up too soon - that the
engine can't achieve higher rpms and its power.
The transmission needs two inputs: throttle position and vacuum for its
vacuum powered shift modulator. The throttle position "tells" the
transmission when to up shift - quick up shifts at light throttle and
delayed up shifts at full throttle. Earlier models had a rod which was
replaced by a cable from the throttle linkage on the top rear of the
The vacuum modulates the harshness of the shifts - soft at low rpms and
hard at full throttle.
It could be that your '82 is more developed than the ones I know, I
don't know each model's modifications.
Unless someone here can help, I suggest you ask a M-B shop to look at
it, not a transmission shop for they just want to sell transmissions!