700R4 Lockup Wiring w/ TBI Control

[Reyals Bemus]

I posted this over on the H.A.M.B. but know there are tons of knowledgeable guys over here too!

I'm working on a '64 C10. It has a later model L31 350, on top of which I am installing a Howell TBI kit & harness. Behind the engine I have a Phoenix Trans. 700R4 that was internally wired up for "one wire 4th gear lockup". What I am trying to do is re-wire the transmission to work with the TBI lockup wiring. I've talked to both Howell and Phoenix about it, but neither were very helpful in explaining what needed to be done to make it work.

I've taken care of the VSS signal with a JTR 2-pulse unit (found here: http://www.jagsthatrun.com/SpeedSensors_Order.html).

The Howell TBI wiring harness is, according to them, exactly like factory when it comes to the TCC wiring. There are three wires going to the transmission- a purple, tan, and light blue wire. Purple connects to terminal A, light blue terminal B, and tan terminal D.

The problem is that I am not sure how to rewire the inside of the 700R4 to revert back to factory TBI lockup control. I spoke to one guy at Phoenix who told me to replace the 4th gear pressure switch (self-grounding, one post) that they installed with a two post unit which will allow me to send a ground wire back to terminal D. I've done that, and now I have two wires running from the transmission up to the connector. A wire comes in from terminal A, routes through the lockup solenoid, up through the new two post 4th gear pressure switch, then back to terminal D. But what about that third wire, the light blue one at terminal B? Where should that connect to inside the trans, and/or does the TBI ECM need it in order to lock up the trans? I actually only want 4th gear lockup, not 3rd and 4th, like I think I read was factory.

If I understand correctly, the purple wire is merely a 12v supply wire that is routed through the brake switch and then down to the transmission. When I look at a TBI ECM pinout diagram, I find that the tan wire comes from A7 labelled "TCC", while the light blue wire comes from C7 labelled "HIGH GEAR IN". I can't make sense of what this means exactly. Can anyone help me out?

I currently have the pan off the trans as I recently made the change according to the Phoenix trans guy. I can take pictures of anything as needed.

Update: I just spoke to Phoenix Trans. again, and they said that that light blue wire does NOT need to go to anything in the transmission; the ECM will still be able to provide lockup. Can anyone confirm if this is correct?

[Bigdav160]

IIRC, the 4 gear switch is a computer input

[Mikebleedsgmc]

Old Thread revive! 89 700r4 tcc wires.

[VetteVet]

Originally Posted by Mikebleedsgmc

Old Thread revive! 89 700r4 tcc wires.

There is some great information on Youtube. Just type this into youtube search.

700R4 Lockup Wiring w/ TBI Control.