We have a 1973 220 gas sedan with an automatic transmission.
When starting out from a stop with light throttle, the transmission feels like it shifts at 5 m.p.h.
It then shifts at 15, 25 and then 35. It makes no difference what position the throttle is in, it shifts at these speeds, unless the car is getting some heavy throttle.
The shift at 5 m.p.h. seems strange, almost like the torque converter is locking up. The other shifts are crisp and the transmission does not slip. Are these the characteristics of this transmission? Possible modulator problem? Thanks for any suggestions!!

Greg

There is throttle pressure linkage on that model. There is a linkage between the throttle and the trans.

Changes in throttle should change the shift points. Shift timing is a control pressure problem not a modulator one.

Shift strength is a modulator problem.