700R4 Lockup Control w/ TBI

[matt2491]

You guys MUST be able to help me out! No one else seems to know anything about my problem.

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?

[Fast355]

You guys MUST be able to help me out! No one else seems to know anything about my problem.

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?

High gear switch is a must for proper operation.

Years ago when I switched my G20 over to TBI I used a 1992 C1500 transmission harness from GM and the lockup worked perfectly. To keep the trans cool you want lockup like factory in 2nd, 3rd, and 4th.

[buddrow]

Most of th custom trans swaps I perform is 4th gear engagement type. Meaning, i have it wired similar to how ur trans came. Its easy and functional. If u wish to have a vacuum interupt u can wire one inline with the 12v to pin A at the trans but i find in most situations its not necessary. I wouldnt worry too much about all the extraneous operating conditions with different switches. Fyi i believe the blue wire may be for the factory temp sensor inside the trans used to inhibit tcc operation until trans temp is correct. Either way i stand by the 4th gear setup for ease of use. Never had any complaints or problems with that setup. HTH

Buddrow

[Fast355]

Most of th custom trans swaps I perform is 4th gear engagement type. Meaning, i have it wired similar to how ur trans came. Its easy and functional. If u wish to have a vacuum interupt u can wire one inline with the 12v to pin A at the trans but i find in most situations its not necessary. I wouldnt worry too much about all the extraneous operating conditions with different switches. Fyi i believe the blue wire may be for the factory temp sensor inside the trans used to inhibit tcc operation until trans temp is correct. Either way i stand by the 4th gear setup for ease of use. Never had any complaints or problems with that setup. HTH

Buddrow

The temperature switch on the 92 setup I worked with did not inhibit the TCC it force locked the TCC at about 220°F. With the 2,800 rpm stall and towing in hot weather in stop and go traffic it would sometimes enable lockup right after the 1-2 shift and keep it locked. This was with a properly plumbed 20,000 lbs gvw cooler as well.

[1v6pony]

Ok you and I are working on almost the same thing, I also am having trouble with mine.
It sounds like you have the Type 5 wiring harness in your trans. To identify this if you have three pressure switches on the Accumulator side and the one closest to it is a single terminal then you have a Type 5 Wire harness And the D terminal is a ECM ground and if you switch this out to a double terminal switch, you will also have to rewire all the other pressure switches... as the power path is different... I am dealing with the opposite, Howel supplied me with a ECm set up for a 5 wire harness and the internal in mine is a Type 1 wire harness... I am going to call them in the morning and see if it can be rectified by them or if I have to replace my Double terminal with a single terminal and get A new internal wire harness to fit.... It is very helpfull to have a ATSG of the trans and also know the year of the trans. Another way to find out if you have a type 5 harness is the solinoid ID Type 5 should be a Blue insulator or ID number of 4125... So in nut shell if is not as easy as just changing the one pressure switch..
Hope this helps and i hope Howell helps me out ....

[buddrow]

You can also eliminate all but the power wire to the trans and run a 4th only lockup setup. I do this on just about every 700 retrofit for ease of installation. Some changes are required to the internal trans harness but very simple i u can crimp a terminal. ;) if you would like i can supply you with schematics.

Buddrow

[1v6pony]

You can also eliminate all but the power wire to the trans and run a 4th only lockup setup. I do this on just about every 700 retrofit for ease of installation. Some changes are required to the internal trans harness but very simple i u can crimp a terminal. ;) if you would like i can supply you with schematics.

Buddrow

I will take the info, If t might be my only choice, I will know more after I talk to Howell Eng.
Note: My trans is a early 1986 no Aux valve body
Thanks

[EagleMark]

Howell is pretty good with taking care of customers and wiring, may be an easy fix for you without mailing? Some have reported their re-tune end is not so hot anymore on OBDI stuff.

But 4th lockup only is also a good thing and all that is really needed. Way less TCC heat and wear. I only use 3rd TCC lockup because of the 3:73 gears and small tires so a lot of in town driving is 3rd and lock.

[1v6pony]

Howell is pretty good with taking care of customers and wiring, may be an easy fix for you without mailing? Some have reported their re-tune end is not so hot anymore on OBDI stuff.

But 4th lockup only is also a good thing and all that is really needed. Way less TCC heat and wear. I only use 3rd TCC lockup because of the 3:73 gears and small tires so a lot of in town driving is 3rd and lock.

Note sure what would be best for me
33in Tires and 4:11 gears 4x4 used mostly not offroad but daily driven.
Thanks

[buddrow]

4th gear setup is best.in your situation u want as much torque as possible and the converter spinning with multiply what your engine provides along with the gear redutions in 1-2 gears. If you want a solid install without hassle do it, or you can wait for Howell to get back to you, its your call. Not trying to be a jerk just trying to help u make a reasonable decision.

Buddrow

[EagleMark]

33s and 4:11 is a good combo. But you really don't need the 3rd gear to lock, would be better driving and easier on TCC/heat etc... without it!

[lionelhutz]

I guess I'm different then others. I've had a 700R4 that locked in 4th and it sucked to drive. Both the upshift and lockup hit at the both time and it made for a big rpm drop any time I was driving the car easily. Also, I'd have to kick-down the transmission out of 4th to get any decent acceleration once it's locked. I also found the transmission wouldn't downshift early enough when slowing to a lower speed as it would really lug in 4th with the converter locked. It pretty much had to be manually downshifted to keep driving.

The ECM logic will allow it to unlock with some throttle input and also inhibits lockup until above a certain speed. Works way better then just being locked-up in 4th all the time. It stops most of the lugging when slowing from higher speeds too but if you have a decent cam or not enough stall it may still do it a bit.

For the OP, The solenoid connects between pin A and pin D. Pin B should go through a 4th gear gear switch to ground. Pin C7 on the ECM is to switch between using the low gear and high gear logic for lockup. You could leave it unconnected and use the same logic (the low gear) for all gears. If you set the speed ranges right it pretty much wouldn't lock in anything but 4th anyways.

1V6pony - I'm not sure what a 5-wire connector does. Maybe share the ECM you're using?

[1v6pony]

Guy at the trans shop, sugested the same thing get rid off all the switches and go 4th only.
So still waiting on your scematic.
Thanks

[buddrow]

Okie Dokie let me dig it up and I'll post it for you by tomorrow.

Buddrow

[lionelhutz]

Don't forget to include suggestions on how to control this lockup because the PCM won't don't do it.