I'm looking for info on the Factory ThirdGen Lockup system that was installed on EXPORT F-bodys. This set-up was used on cars with the 700R4 but no ECM to control the lock up feature. In the past I had acquired an 84 Trans Am that was originally a Canadian car and it had NO ECM from the factory. I used the Engine/Tranny from that car in a 85 Berlinetta that was converted to analog interior and from V6 to V8. At this point in time there is NO TCC lock-up,..... cause' there's no ECM harness or ECM. I'd like to know if anyone is familiar with the factory GM F-Body system. Here is a pic: Let me explain; There is a single wire leading into "A" pin on the tranny connector. ( would be the Purple wire on all other 700R4 plugs. ) At the C207 connector there are 3 wires that match the corresponding pins on the ECM harness of all other 700R4 cars for TCC control. Green: pin "H" (would be Tan/Black ) TCC control convenience center - Or ECM Lt. Blue: pin "P" ( would be Purple ) Brake Switch Black: pin "M" Black Ground On this set-up you can see the vacuum switch. (There are 2 on this bracket because I BELIEVE the car required an additional vacuum solenoid for the hood cowl ) The vacuum switch has 2 pins and 3 wires..... The Blue wire would be to C207 "P" and the 2 green split off the other pin and go to Tranny (pin "A") and C207 (pin "H") The ground wire at C207 leads to a simple "eye" ground connector that gets screwed to the back of the engine head. This ground appears to be separate from the TCC system and would provide ground to whatever is on the other end of the dash harnesses C207 pin "M". How does this system work ?? The Green wire on this harnesses C207 leads to a switched ground on the ALDL - This is the same switched ground circuit provided to the tranny to activate TCC in the ECM systems. ( the same one that gets switched ground by a custom installed toggle switch for manual TCC control ) How does this set-up know when to apply the switched ground ?? The vacuum solenoid COULD be grounded when screwed to the body - I don't know ! This is a diagram I made showing the system as it is "in my hand"; My concern is this : There is no 4th gear indicator in this system. How does the tranny know that it's in 4th gear in order to apply TCC ? ( maybe it's applied in all gears ?? ) What are the vacuum ratings that will allow the solenoid to provide switched ground and activate the system?? ( I was under the impression that the vacuum solenoid was used as a "Cut-off" during high vacuum - or heavy load - conditions,......... and that's confusing me. The solenoid appears as if it's actually a "cut on" by providing switched power !?!?! P.S. The tranny and the vacuum Lock Up were taken from the same 1984 EXPORT car. I understand there are differences in the lock-up INSIDE the trannys over the years, but that doesn't matter in this case. The engine tranny have been installed in my 85 Berlinetta for over a year and about 1200 miles without Lock-up installed. ( & no ill effects - yet. ) Anyone have any input ??

In the 700R4 there is a location for a 4th gear pressure switch (on the valve body). I know that the ECM'd cars use this to change which set of TCC tables to use. The 4th gear switch status is sent to the ECM.

This pressure switch can also be wired in series with the TCC solenoid to provide lockup only in 4th gear.

The 700R4 can't lockup in 1st for mechanical reasons. So it is also possible that the export setup allows lockup in 2nd, 3rd, and 4th. In this case the 4th gear pressure switch wouldn't be used.

RBob.

If you'd rather buy the best than figure it out, lemme say that 4 times I've used the PainlessWiring kit. It currently sells for over $120, but I truly love it. It includes everything, and it locks up, in OD only, when there's enough vacuum for the vacuum switch they include. When you give it gas, it unlocks. When you apply the brakes, it unlocks. When you go to any other gear, it unlocks. Truly excellent.

Thats the same system my 1983 G20 Van had from the factory. The valvebody should have atleast a pressure switch tied to 4th gear. The vacuum switch will lock the converter in 2nd and 3rd gear as long as it is recieving a decent vacuum signal (PORTED, PORTED, must I stress PORTED vacuum and it needs a delay valve in the hose). 4th gear lockup was controlled by the 4th gear switch in the transmission and over-rides the vacuum switch in OD. In OD, unless you are stepping on the brake, your are in lockup. My valve body had a secondary pressure switch that was for the 3-4/4-3 shift and cut power to the TCC during downshift/upshifts. I should also mention that the EGR signal was bled from the EGR valve by a solenoid that vented it to a port on the back of the carb when the transmission was in OD.

I've tried Painless' kit with both ported vacuum and manifold vacuum, on each car I used it on. Every time, same conclusion. Manifold vacuum. NOT ported.

Fast, I always wondered what the pulse pressure switches were for. Now I know. The 700R4 has locations on the valve body for various pressure switches, but are not always tapped for them. Such as the '92, only has a 4th pressure switch along with a temperature switch to force lockup in 4th when the tranny temperature goes too high.


For the vacuum TCC lockup on the export system, it could be either ported or manifold vacuum. There will be a difference is how the transmission feels to the driver. This is an area that I played with in the ECM calibration, which is the same difference between ported and non-ported vacuum.

With an ECM setup there is what is known as coast-release. Whenever the throttle is closed the ECM unlocks the TCC (in most/all? calibrations). As the throttle is then opened the TCC locks back up. The driver can usually feel this, and some don't like the way it reacts.

With the 700R4, when the stick is in OD/4th, the overrun clutches are dis-engaged. So on a closed throttle there is no engine braking.

When the stick is in the D/3rd or 2nd position the overrun clutches are engaged.

In this case if the TCC is kept locked when off the throttle it feels like a stick tranny. There is quite a bit of engine braking. With the TCC unlocked there isn't any engine braking.

So the difference between ported and non-ported vacuum to the TCC lockup vacuum switch is along the same lines. Using ported vacuum is similar to how the ECMs are set up. There will be a TCC coast unlock (vacuum ceases).

If using manifold vacuum the TCC will stay locked. Until either the brake pedal is used or the tranny downshifts into 1st. In this case engine braking will occur if the selector is in D/3rd or 2nd.

Can try it both ways and see which works best for your setup.

RBob.

My Van never handled manifold vacuum lockup at all. It caused the TCC to stay locked and bogged the small 305 on initial tip-in from a roll.

I haven't connected all the dots - yet; But I'm getting close ! Thanx for the input guys !

I have located a few more tidbits of info that help to complete my riddle. In the 1984 Camaro Shop manual there is a description of the vacuum controlled TCC as well as a block mounted temp switch. Here are those images:






Both switches look similar to the pictures. The Cold Override has 2 pins on it (wire colors are Orange and Black/Red stripe). I found the C/O switch still connected to the 84 Trans Am engine harness. I have not been able to trace the 2 wires yet. I also found this diagram located inside the 1986 Firebird Shop manual:



I knew that not all 700R4's were the same - but I had no idea they were so different !! This "Type 12" version of the tranny was the only version of the various types that shows a single wire input at tranny connector pin "A".

I have yet to see a factory diagram that includes vacuum and I have yet to locate a factory wiring schematics that includes the Vacuum TCC switch or the Cold Override switch. But I'm taking advise and still learning more........ Thanx for the help !

The cold override switch is new to me, so thank you!

Gas Engine vehicles had a cold overide as well. It was a TVS, Thermal Vacuum Switch, which blocked vacuum from reaching the vacuum switch until the engine warmed up to around 110-120*F. I live almost right off the service road of a major highway. Jumping on the highway on a cold morning meant I drove around 2-3 miles @ 70 mph, before the converter would lock.

I could not resist - I traced the wires on the Firebird harness. It appears as if the TCC vacuum harness is complete and should function correctly as pictured above. Since all parts are from the same car they should all interact with each other the way they are supposed to. ( no worries about if the tranny knows it's in 4th or not ! )

The Cold Override switch I found was used to control the hood cowl. I followed the Cold switch Orange wire back to the oil pressure (oil pressure-send signal to cold start.) I followed the Black/Red wire from the Cold switch to the connector for another Vacuum Solenoid. ( high vacuum-send signal ) I then followed that wire from the Vac. Solenoid to the hood cowl connector. ( Open hood flap.)

The harness in my picture above appears to be the only parts of the TCC system for MY application. The Diagram I made also seems to be as accurate as possible for a "Type 12" 700R4 transmission.

Once I manage to get this installed I'll report back to let you guys know if it works or not ! Thanx again for all that detailed info !

Quick update / Some notes:

I previously described C207 pin 'P' as 87 and earlier cars have the Brake switch to C207 Pin 'P'. 88 and up ( I believe ) the Brake Signal to the TCC ( purple wire ) runs to C100 @'E7'.

The System is installed and I have TCC operation. It was not operational when it was simply "plugged in." TCC system is from an 84 Trans Am with matching 84 TA tranny. The car is 85 Berlinetta, non-ECM 305 with an 85 V6 Engine harness & 88 Coupe interior dash harness. When I first drive the car after installing the TCC I felt nothing. (In my haste to install I didn't notice the difference in C207 'P' ! ) I just re-pinned C207 and spliced into the brake switch ( purple ). I then installed a courtesy light under the dash that was grounded to the body and spliced into the Green tranny wire Leading to "A" on the connector.....

Operation:
* System is hooked to PORTED Vacuum

TCC light gets power in ALL gears. ( regardless of shifter position.) Whenever the Brake pedal gets pressed; power is cut-off. Anytime the gas pedal is pushed to part throttle the Light comes on....... Take your foot off the gas ( at ANY speed in ANY GEAR ) and the light goes out.

From a stop: Press the gas JUST enough to get the car rolling and slowly build momentum,...... (a couple hundred RPM over idle) The TCC light Waits to come ON till second gear at about 1200 RPM

From a stop: Any Gear, Part throttle,...... The TCC light will come ON right away and will stay on until you let of the gas ( "Coast mode" )

While driving: Depends on Manifold vacuum at that time,..... Floor the pedal and the TCC Light goes out. The TCC light WILL come back on while your in WOT ( after vacuum builds up again ?)


When driving at a cruising speed and 'bumping' the brake there is 2-300 RPM bounce in the tachometer and it does have that stick-shift "feel" to it at lower RPMS. I didn't drive a lot so I didn't have a lot of time to test, but that's what I took from my ride !

hi , i am presently removing my 700r4 on my camaro 85 350 and installing a T5...i want to remove this tcc lock up ..it has a one wire plug to the 700r4 that goes to the solenoid,,,on the solenoid it has another plug with this white wire..can i cut this?...do i need any of this for a T5 setup?,,thankyou.

There is no switched ground in that setup. The lockup of the TCC is mainly controlled by governor pressure on the TCC valve.

so basically i can removed this unit without any issues since i will have T5?..thanks.

After you have the T5 installed, yes.

Mario - Could you post a picture ????


Ya', When I first looked into the system I didn't know anything about it,... That's when I asked about switched ground. By the time I was done I realized that the system always had power, that the solenoid cut power based on vacuum, and that the brake toggle also used switched power to override the solenoid.

Looking at the tranny diagram, and after testing the system before and after installation of this set-up, I would find it hard to believe that factory non ECM cars used anything other than an electric signal to operate the TCC. It's vacuum operated, but the vacuum is simply used as a switch to turn the electricity on and off. It's power at pin 'A" that locks-up the TCC.... No 12 volts; no TCC lock-up. Sure the tranny internals are probably dependant on each other to operate, but this post is more about the external system and operation rather than the tranny internals.

It's almost worth thinking of it as the TCC will lock itself up by the hydraulic circuit in the transmission over a certain road speed, and the electrical circuit is there to unlock it during certain conditions.