Me and my father have a 67 GS with a turbo 400. The man who built the car passed away ten years ago. We purchased it from his daughter. My question is. There are two toggle switches mounted on the console. If I flip either switch the transmission will not shift out of first. I even tried to shift it manually but it wont let me. Any Ideas what these might be. My neighbor behind me is a gm transmission man. He said it looks like a standard T 400. He even went underneath the GS and looked.
If the switch applies 12 volts to the downshift tang on the driver's side of the transmission, the transmission will only shift at wide open throttle. Shift RPM will be determined by the governor. Have a look at the ID tag on the passenger side of the transmission case. A 67 GS should read 67 BA on the tag. If it does, it is a switch pitch. The other toggle switch is probably for high stall. If you remove the electrical connection on the side of the transmission, there will be 2 tangs, one vertical (kick down), the other horizontal (switch pitch).
Remember the 2 tangs on the driver's side of the transmission I was talking about? One controls the kick down (vertical tang), the other is for the switch pitch (horizontal tang). Apply 12 volts to the kick down tang, the transmission down shifts. The 12 volts is passed down to the transmission by a throttle linkage mounted switch. That switch may be gone now. That same switch controlled the switch pitch. The switch pitch transmission was used in 65-67 Buicks. It was a THM 400 with a special front pump, input shaft, and torque converter. The converter had a stator with movable blades for 2 different stall speeds. A piston concentric with the converter hub moved the stator blades. A solenoid in the front pump directed fluid to and from the converter via the input shaft. Apply 12 volts to the horizontal tang, you get high stall. Remove the 12 volts, the converter goes back to low stall. That may be what those 2 switches installed in your car are for. One is for kick down, the other for stall change. Each switch applies 12 volts to the 2 tangs. You should easily be able to verify this with a simple test light. The Switch pitch transmission will look externally like any other THM400. The differences are internal. Get me the 2 letter code on that ID tag. Here is a visual thread on what the switch pitch front pump and converter look like. http://www.v8buick.com/showthread.php?143723-VP-converter-Trans-visual-ID-guide http://www.buickperformanceclub.com/switchpitch.htm
Sorry it took me so long to get back. It is a switch pitch. I have a stupid question. I know you want to use the higher stall for drag racing. Would you switch it off after you hit third? Also would you switch it off for high way driving?
The switch pitch is a great tranny in my opinion. For racing, we had high stall on manual switch and released it at 60' mark. In my convertible, I set it up on high stall when brake lights on. So at idle, or stopped, it is high stall. A short delay lets it release to regular after I get rolling.
