'89 chrysler lebaron convertible

Does anyone know where to find the transmission modulator on this car. I am thinkin that it is not engaging first gear, as when I go up an incline from a stop, it shudders real bad and almost won't pull the hill :banghead:. It does it a little when already going, but from a stop it won't, and I can't find the car book for it.
Thanks,
Schellfishy