7427 install, first impressions

[EagleMark]

TH400 Kick Down switch is used on '427 PCM conversion to kick down a TH400 like the old 1228747 ECM did. The '427 PCM can't send "ground / battery negative" to the TH400 kick down relay like the old 1228747 ECM did.

dave w

Do you have any wiring info on this to 1228747? We are trying to figure if 1227747 can be swapped in it's place...

[dave w]

Do you have any wiring info on this to 1228747? We are trying to figure if 1227747 can be swapped in it's place...

So I'm wanting to make sure I understand the question. You need the '8747 TH400 Kickdown Relay Wiring schematic? You are swapping out an '8747 and installing a '7747? I have schematics on my home computer, but I'm at work now. Later this evening I should be able to post back the '8747 TH400 Kickdown Relay Wiring. The parameters for the '8747 TH400 Kickdown Relay are different than the '7747 TCC lock / unlock parameters. I think if I were to swap out an '8747 and install a '7747, I would install a TH400 gas pedal kickdown switch to send ground to the TH400 Kickdown Relay.

dave w

[EagleMark]

Yes I'd like to have them as I don't know how it works and would like too!

Thanks for the info! So same switch in trans would work triggered elsewhere? Right?

[dave w]

Yes I'd like to have them as I don't know how it works and would like too!

Thanks for the info! So same switch in trans would work triggered elsewhere? Right?

The attached wiring schematic shows both the TH400 Kickdown Relay and the TCC wiring. Pin A7 on the '8747 is wired as either AT Kickdown / Shift Light (manual trans). Pin A7 on the '7747 is wired as either TCC / Shift Light (manual trans).

The pictures below shows a TH400 accelerator / gas pedal mounted kickdown switch. I would image most any junkyard that specializes in light truck would have a TH400 accelerator / gas pedal mounted kickdown switch.

The wiring is very basic. Remove Pin A7 from the '8747 and connect the wire from Pin A7 to one (does not matter which one) of the termianls on the TH400 accelerator / gas pedal mounted kickdown swich. The other terminal of the TH400 accelerator / gas pedal mounted kickdown swich is wired to Battery Negative. Adjust the TH400 accelerator / gas pedal mounted kickdown switch as outlined in a GM service manual. Sometimes a thick rubber hose needs to be installed on the tan plastic plunger of the TH400 accelerator / gas pedal mounted kickdown switch to get the kickdown where you like it.

dave w