Switch pitch 64-67 cars and 65-7 in a 400 tranny. http://www.buickperformance.com/switchpitch.htm The standard rear in a Riv GS was a posi.
Switch pitch If you meant how can you tell if it's a switch pitch by looking at it, it will have the extra plug for the switch from the throttle. This will be on the drivers side of the tranny in the general area of the speedo cable inlet. It will have one vertical and one horizontal mate for the wire which would have come from the engine.
Careful! Most 75-76 400's have a second plug for transmission controlled spark, but they're not SP. If you see the "heel mark" tranny pan as well as the second plug then you're OK. The heel mark was the results fo the type of filter used in the mid to late sixties, but was switched by 1970. Since transmission controlls sparck wasnt around at that time, you'll never see these two together...unless of course someone was messing with the reansmission. Good luck!
Transmission controlled spark I thought those harnesses only had one wire going to the transmission. That's why I described the switch pitch as a two wire setup with one vertical and one horizontal. Did they have the same kind of connector on the transmission as the switch pitch?
Re: Transmission controlled spark Yes, the horizontal was connected to a pressure switch on the valvebody that signalled the thermovacuum switch on the intake manifold to allow spark vacuum advance in high gear. On a switch pitch trans, the horizontal connection energizes the stator solenoid for a stall change. If the trans is a 65-67 model and it has 2 connections, it is probably a switch pitch. If it is a later model, maybe not. If the input shaft of the trans is visible, it is easy to see the difference between fixed pitch and variable pitch transmissions. The stator splines on the switch pitch are about 1/2" long. In a fixed pitch trans, they are 1" long. Also, if you stick your fingers into the converter hub, and can feel the teeth, its a fixed pitch. The teeth on a switch pitch converter are too deep to feel.
Thanks! Thanks everyone! Not sure of the year, but there's a Riv GS in a boneyard that's mainly a F**d yard. I thought about grabbing it because I couldn't let something with class set there amongst the "junk":grin: . P.D.
