Bought a built 4l80e off craigslist a while back and took the pan off it today to make sure it was what they said. Everything looks like new and in great shape, however there is a sensor with nothing plugged into it. It is over by the dip stick, what is this sensor for? I don't even see any wiring that would plug into this thing, do i need it?

I circled the sensor i'm talking about in the pic, and the arrow is pointing to where the dip stick goes just for reference.

 

Dummy temp sensor, disregard it

 

ok, good to know, and i won't worry about it.

One more question. When i put the pan back on, do i need a gasket to seal it up for proper clearance? or can i put it on with out gasket and just use rtv?

I hate using cork gaskets as it seems like they all eventually will seep.

 

I recommend the gasket. I prefer fiber over cork, but the cork should be just fine