I was under my car(86 T/A w/89 drivetrain)to pop on my shifter linkage and I noticed the plug to the trans(driver side 4 prong)was unplugged, I tried like hell to get it back w/no luck. Is that the plug for the o/d? My speedo works. If I leave it unplugged would it hurt anything? Also is there a way of getting that sender out of the trans while it's still in the car(trans)?

 

It's not a sender, just a recepticle (wires on the other side connect to a couple pressure switches and the TC solonoid. Anyway, it's probably not plugging in because the recepticle has dirt or something clogging it (assuming it's been driven with the plug out). Try hitting it with some compressed air then plugging it in. There's a locator tab too, since it'll only plug in one way. If you leave it unplugged, the TC won't lock up, and some people would argue that that causes heat and a shorter lifespan for the transmission. It definitely causes a 2-3 mpg drop in your fuel economy.
If you still want to take the recepticle out, you don't have to remove the trans from the car, but you do have to drop the pan, and it's held in with plastic expansion tabs that you just squeeze (I think you can use a 12-pt deep socket of an appropriate size) and push it back out the hole. There's a gasket you'll have to replace as well.

 

OK great! Thanks for the info! That's what I thought it might be for. I'll try to get some of that canned air. Thanks for the help.