I got a screamin' deal on a 700R4 that has been built up. It has zero miles since rebuild. It was fitted with all TCI internals, including the reverse manual valve body. My question is whether or not the ECM can still control the lock-up converter? I went to TCI's website and looked at the instructions for the valve body kit. Nowhere in it does it say anything about using it in a vehicle that came with the 700 tranny originally. They show to wire in a TCC switch. I even called up TCI and asked them. The tech seemed pretty ignorant about the wiring aspect of their kit. He said the kits were primarily designed for aftermarket racing use. Does anyone have any knowledge of this valve body? I still want the ECM to control converter function.

 

Here is the wiring diagram TCI has in the instructions. Wouldn't the Red wire (A) be the GM Purple wire, Green wire (B) be the GM Tan/Black wire, and the Black wire (D) be the GM Dark Green wire? Maybe I'm not seeing this right, but it looks to me like it should plug right into the factory ECM and work just fine. The two grounds with switches would be going to the ECM, which would control the opening and closing of the switches. Right?

 

Nobody is familiar with the wiring for 700R4 tranny?

 

Looks to me like that diagram is for non and ECM controlled 700r4's. Normally - you wont have 3 wires.
The Bottom ground connection is what the ECM uses to energize the solenoid in 4th when it gets in that gear. Just like a regular solenoid - red and black - power and ground on/off, etc.. The middle wire is most likely for manual control of lockup for non-ECM 700r4's, or for user manual lockup via a switch somewhere in the cockpit to force lockup if you want. So i believe you're on the right track. I'd bet the ECM ignores the middle wire (unless its manually switched), and just plugs right in and uses the red & black connections. If you want lockup on-command, the middle connection would allow you to override the lockup whenever you want, and when you switch it back off, the ECM would still control it normally. If you did that with a 2-wire system, as soon as you switched it off, the ECM could no longer lock it up.

Plug it on in! Im no 700r4 guru, but the circuit diagram pretty much explains how it's designed to function and i cant see a problem with proceeding as you see it.

 

There are 3 wires in the factory ECM setup. TCI is using the same pinout as the factory wiring harness, but the thirdgen ECM expects the 4th gear switch to be normally closed, not normally open as in the TCI setup. You might want to drop the pan and change the switch.

 

So the ECM does all of the grounding from pin B, and just uses the 4th switch to know when the trans is in 4th?

 

Now that I look at the diagram when I'm awake I notice some differences.

In the factory thirdgen setup, power is applied to pin A through a N.C. switch on the brake pedal to force the TCC to unlock during braking. The ECM (or vacuum switch if your car came without an ECM) grounds pin D to lock the TCC. Pin B is normally grounded through the 4th gear switch inside the transmission to let the ECM know when the car is in 4th.

 

Ok - thats got me interested Makes me wish i knew more about the 700r4.

Question though - how would pin B being grounded let the ECM know it's in 4th? Doesn't the TCC lockup in other gears as well?

Based on the diagram's logic and your comment, i'd think the ECM is not checking to see when the TCC is to be LOCKED, rather it's checking to see when it should be UNLOCKED. Basically, that changes my outlook on the ECM's side of the picture. The TCC is normally locked unless the ECM tells it not to be.

That makes a lot more sense.

That would explain all the threshholds set for TPS, vehicle speed (the only exception in this case would be the speed-controlled lock/unlock settings), but things like A/C clutch will lock it, TPS above/below a threshold, engine overheat even.

Sorry Boxeat2469 - i wanted to help you out when nobody else answered, but that last post got me thinking of the control-side of the logic. Im thinking the 700r4 is normally "energized" until it's told to "de-energize". In that case, the pinouts make perfect sense. A is power or other optional conditions (maybe hard logic...such as A/C clutch on/off? Or some other manual intervention), B is control signalling (telling the TCC that it should unlock now because you just sent the TPS to 80% for example), and D is strictly for vaccum or 4th gear...but still B has the ability to bypass it. Maybe VSS controlled? To prevent chattering, it includes the 4th gear switch in addition to the vaccum for non ECM cars?

Where's the 700r4 experts? Im curious.

 

That diagram is how TCI has you do it when the reverse manual valve body is installed. There is no ECM. Wire A is hot, B is a dash mounted switch so you can manually control converter lock-up, and D is connected to the 4th pressure switch so the converter will lock automatically when you put it in 4th. Using that wiring, the ECM would not control the converter at all. This diagram is how the factory setup works. Again, wire A is a hot wire, B goes to the ECM so that the ECM can decide when to lock the converter, and D is for the 4th gear pressure switch. When the trans goes into 4th, the switch opens. When the ECM detects that the switch opened, it knows the trans is in 4th gear.

 

Pins B and D are mislabelled in that diagram. The factory F body harness in the 700R4 also has a 4-3 kickdown switch to disengage the TCC before downshifting to prevent overly harsh 4-3 shifts.

There were literally dozens of different wiring arrangements used in the 700R4 for each application. The transmission my car currently has is a 4L60 from a 1993 Caprice Police Car. The 4th gear switch in its harness is N.O., not N.C., and it also has a temperature switch to force the TCC to lock up if the transmission fluid gets too hot.