FAILSAFE is a much abused word. It is very dramatic because it combines the apparently contradictory concepts of failure and safety in a single word. The reality is not so dramatic.

An aftermarket shift kit would be the easiest way to do this project, if you didn't want to just figure it out for yourself.

There are solenoid operated valves controlled by electric timers and float operated valves that do not require power (similar to steam traps). Neither work in freezing conditions.

MESC SPE 85/200 was a mere listing of many types and brands of packings (probably built upon some kind of survey in the warehouses of the manyShell plants all over the world.)... but may be in the mea

Solenoid valve coils have a surprisingly high inductance and can generate interesting transients when de-energized.

The necessary effect (or power consumption and power peaks) would principally be a combination of many factors, main beeing the pressure class rating of the solenoide valve

All solenoid valves normally closed, open with electrical current. All pneumatic operated valves, normally closed (by spring) opens by air. Failsafe all: closed (by no air and/or no current)

Spool valve is a sliding cylindrical member inside a block, THere are ports on either side of neutral position.