Electric over air valve.

It uses air to hold the latches closed, or do springs hold the gate closed and only uses air to open it?

Doesn't matter it just changes what valves you need. You can do it with one or 2 solenoid valves, or one solenoid valve and a 4 way inversion valve. It's the same as lift axles and can be done a lot of different ways.

 

use any 12V ABS valve. There are two coils - holding and dumpng air. Use dimping air coil. ABS valves dumps air from air bags in some seconds.

 

when you turnt voltage off valve lets air from levelling valve fill air springs againe, but slower. I usually add two valves for both the sides to lower faster

when you'll get valve on JY post me its brand and number, try to get Wabco, I will tell you what terminals to use