went to look at a 94 c280 auto with the 722.4 trans, drove it and when in p r n it worked fine as intended. put it in d and the engine won't rev past 1500 rpm and it won't shift. was thinking about a modulator/governor issue or is it something more serious?

Probably won't shift because it's not supposed to shift at only 1500 rpm, at least when cold. You need to figure out why it won't go over 1500 rpm first. Maybe clogged cat.