G'day, I was talking with a mate the other night about intercepting the signal from the ECU to the gearbox and altering it for full manual gear control.

I know you can select 1, 2 and 3 with the T-bar but you can't get control over more than telling it not to up shift over whatever gear you've selected.

I read from one of the ECU wiring diagrams that there's a wire out from the ECU to the gearbox using PWM signals, a few for the various solenoids and transmission position.

However that's the 6 cylinder ECU, which is great news for my mate but what about the V8's? the only wire mentioning anything transmission related is a single PWM signal.
The V8 is in a DCII LTD, as far as I know the transmission control module was only used in the EBI/EBII V8's?

What me and a mate want to do is have a switch so you can switch to a control box so the driver can input via a button (push button marked 1 for gear 1, button marked 3 for third gear, etc) and the control box would output a PWM signal to the gearbox.

What I need help with is:

How does the V8's control the gearbox (DCII)?
Which solenoids do what

Any help would be really appreciated, it would be a pretty cool little project to do for the times when you want full control over gears.

interesting i had never thought of that but im keep to know more