I have a 63 with the pushbutton 727 transmission.
The Drivers Manual says you can push start it.

I rolled down a hill in second and the motor started at about 27 mph.

Is it OK to do this or is it harmful?

It's not in any way harmful to my knowledge. The rear pump in pre-66 727's (wheel/driveshaft driven) allows the trans be pressurized and operational with the motor "off", so putting it in drive spins up the crankshaft.

D/W

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If it ain't broke, fix it!

Doesn't hurt it at all, they were designed to do that. That was a nice thing about many auto transmissions, back in the 50's and 60's. The torqueflite trans lost this feature after 1965, when the rear pump was removed.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
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