I'm doing an LS and an auto to t56 swap on.a 90 RS... According to diagrams posted in this thread and elsewhere, VIN E cars (TBI) have both auto and manual wiring for the neutral safety switch?

https://www.thirdgen.org/forums/interior/751381-neutral-saftey-switch-wires.html#&gid=1&pid=2

I have found purple and tan/white wires on both the auto shifter and another unused pigtail up under the driver dash. These seem electronically connected via a continuity test I did. Can I use either set? Will this work? How does this work and why only on VIN E cars?

 

It works because they are the same electrical point: you can plug a switch into either one, and it will complete the circuit. The wires that appear at the auto shifter are merely longer than the others, an extension, if you will.

Can't help you there. I'm not sure that's even correct. All cars with manual/auto options, where the auto has a floor shifter, use some variant of this. Not just F bodies, not just GM. My VIN 7 (83 L69) car has the same thing for example.

 

Ok. I have just seen a wiring diagram or 2 that have a manual diagram, an auto one, and a "vin e" that shows both. I'm not sure where these came from. Thanks.

 

Not sure why the VIN E would be any different than the others as far as a neutral safety switch. I've never seen a neutral safety switch on any T5 manual in an F-body. The neutral safety switch on the automatic shifter should be the same circuit as the clutch safety switch on the manual transmission setup.

 

Right: the transmission has no facility that would support that.

Right: electrically, they are the EXACT SAME thing. Just located in the 2 different places, as the OP's resistance measurements and my comments both indicate. I think the OP just didn't quite make the correct connection in the terminology.