19840300D Hard Shift

Not unusual to have hard shifts when cold. The softness of the shifts is vacuum controlled by a "modulator vacuum control valve" on the aft end of the injection pump.

The principal is: maximum vacuum at closed throttle, declining continuously with throttle opening to no vacuum at full throttle. Soft shifts on light throttle and hard shifts at full throttle.

So, if there's insufficient vacuum or a vacuum leak the shifts will be hard. (Incidently, insufficient vacuum will also prevent engine shut down, but that's another subject.)

After all these years the vacuum lines may be dirty and clogged - that's a possibility that should be considered.