Ingar, Norway

I'm close to finishing my 700r4 conversion, but believe it or not, I'm still working on the lockup wiring.
What I found so far is that what I thought was a temp sender is the 4th gear switch. (Blue terminal) Reason for this confusion was that this switch is normally closed and tested as some kind of a PTC sensor...
Opens at 30psi.
My conclusion is that the 4th gear switch is normally closed in a computer controlled system (TPI), else its a normally open type.

If possible, I would avoid to have to change the switch when installing TPI later.
It would be nice of somebody with a 700r4/TPI system can explain how they did the internal trans wiring. Especially if they have moved from carb to TPI.

The other switch appears to be a 4-3 downshift switch. I don't know what it's supposed to do. Its in series with the lockup solenoid.
The switch is faulty, always open. Bad news since it means that the lockup has been out of function on the trans I bought, assuming it would run hot without the lockup.

Apeiron

Even on computer-controlled cars there's a difference in how the transmission switches are arranged. Most TPI F and Y bodies will have a "Type 4" wiring harness, which has a normally closed 4th gear switch, and a 4-3 downshift switch. The downshift switch is to unlock the TCC and prevent an excessively harsh 4-3 downshift.



My Camaro has a 4L60 from a 93 Caprice, with "Type 18" internal wiring. The 4th gear switch in this arrangement is normally open, so I was able to connect the car's stock vacuum switch between pins B and D to automatically control lock-up in 4th. This transmission also has an internal temperature switch to lock-up the converter at all times in 4th in case of overheating.



[Modified by Apeiron, 7:30 AM 1/7/2002]

Ingar, Norway

Thanks a lot Apeiron! That drawing was really useful.

Means that I would have to make an interim solution before I switch to TPI. I'll add a NC relay controlled by the 4th gear NC switch.
(To use a 4th gear NC switch with carb setup that requires a NO switch)

Is that 4/3 downshift necessary? Since mine is faulty I would have to get a new one, not easy over here...

It's not shown on my drawings for 86/88 TPI. Bowtie doest show it at their drawing either.

Jvette73

There are two pins on the 700r4. One is for the 4th gear automatic lockup circut. When this circut is energized, the convertor will lock only when the trans is in 4th gear. You can run a toggle in this circut if you want. When you disable the 4th gear circut, the convertor will not lock in 4th. Sometimes this is handy since it will allow you to cruise in 4th gear at slow speeds while avoiding the bog that can come when the convertor locks up. I keep my convertor unlocked for anything under a steady 50mph.
The second pin is for the manual locking of the convertor in 2nd and 3rd. If you want the ability to lock in 2nd and 3rd, feed this pin through a second toggle switch. The biggest advantage of locking in 2nd and 3rd is better ET's. I gained two tenths better ET with convertor locked in 2nd and 3rd. After doing my burnout, I flip the toggle for 2nd and 3rd lockup. The convertor always stays unlocked in first. When I leave the line and rev through 1st gear, the convertor will lock as soon as it hits 2nd, and remain locked through the 2-3 shift and on to the end of the track.

Apeiron

You could probably live without the 4-3 switch. Leave it out and worry about it later if you need it.

Apeiron

JVette, that's how bowtie overdrives wires their 700's, but you'll never find a factory setup like that. If you try to use one of their transmissions with a factory computer you'll just blow fuses.

Jvette73

Thanks for pointin that out Apeiron, mine is a BTO tranny. I thought they were all like that. My bad.