well it's kind of third gen, this about a '82 chevy pickup I pull my 85 T/A drag car with.

what is a "tip-in valve" and what does it do, I just got the truck and am trying to make heads or tails of whats under the hood. I see the vacuum switch for the 700R4 tranny, but there is also another vacuum switch which the diagram under the hood calls the above.

also the truck has dual tanks and it won't switch from one to the other, what is the most probable cause for this. I don't have alot of time to chase problems because I spend all my spare time under the hoods of my two T/A's.

thanks.

 

The tip in switch if this is the one your talking about and I think it is, (TCS) is a POS emmissions piece that is supposed to reduce emmissions by not allowing vaccum advance when the transmission is locked in low gear, also supposed to prevent dieseling.
As far as the tanks go Id test the switching valve down on the PSR side infront of the tank it can go bad so test for power there for both tanks, if it doesent have power replace the switch in the cab thats whats common.

 

this will get locked :-D