so I am dissabling VATS and I clicked off the flag for VATS but there is also a flag that says 4THNO, what is this? should I uncheck this too? I guess I will throw this question out too, the bin file I have has 0.00 listed and the cylinder number constant, shouldn't it say 8? thanks.

 

Only if you want to change the 4th gear switch from normally open (4THNO) to normally closed.

The cylinder number constant of 0 is for an 8 cylinder.

RBob.

 

I guess this begs the question now, what is the 4th gear switch and what is the difference between having it open or closed?

 

The 4th gear switch resides on the transmission valve body. It detects the pressure when the trans shifts into 4th (OD) and either opens or closes. Typically tied to ground (closed) or not (open). This is an input to the ECM so that it knows if the trans is in OD. Mostly used for TCC lockup table choice. Can also be used as a highway mode qualifier and/or SA retard.

RBob.

 

so basically I want to keep it checked if I want to keep overdrive. what happens when you switch to the corvette servo in the trans? would you still want it. was looking at a comparison on bin files for 305, 350, and 350 corvette, and the corvette had this not checked. is this so it would not kick into overdrive in 4th?

 

Overdrive will happen no matter what the computer "wants". I guess if the computer didn't want you the car to go into overdrive it could detect mph and engine rpm, then kill the motor if it saw high mph low revs .... but they don't do that.
The 4th gear switch (physical switch) is different between some transmissions. Some got a switch that was "open" when in 4th gear, while others got one that was "closed" (to ground) when in 4th gear. If you install a transmission that's from that corvette application you just mentioned then you'll need to modify that switch. If you don't the car will run but the tcc will be all fubar. You'll also be confusing the ecm because it'll think you're in overdrive whenever you're in 1st, 2nd, and 3rd gears!