New plug, properly installed and tightened, still leaks. The only thing left can only be the sealing surface of the pan. It's either distorted somehow, scratched or there was corrosion under the plug that was disturbed when you drained the transmission. Thinking logically, it's the pan.

 

Agreed with the Doc. Check the threads in the pan for trash or distortion. If all looks ok, change the pan.

 

This is where pics are extremely helpful.

 

Thanks, was thinking it's got to be the pan. Not sure how to check there threads with it filled up with oil now. Drain bolt (Was clean/ no rust) but thinking the threads are messed up some how. Doesn't make sense, bolt threads on nice, tightens up good but still leaks. I'd post pictures but I'm at work for the next 72hrs. Left a pan under my truck at home to catch the drips... going to buy a new pan on Monday, only option I believe now.

 

Kinda late response but it happened to me one time and I stopped it by giving it a short whack with a mallet. Since the shoulder of the bolt is what seals, I'm guessing the pan warps outward allowing the shoulder to not contact the pan, therefore causing a leak.

 

Sometimes... weird shyiiiit happens. 38 years in the business and I STILL come across things that I can't explain.