solution found

I'm pretty sure that I've found the solution to the wet seat belt issue in the extra cab Tacoma. I don't have the ability to post photos. Open the front and back doors on the driver side. Look at the rubber seal that is attached to the truck body. When you close the back door you will notice there is a piece of the rubber attached to the door at the top that actually creates a dimple in the rubber attached to the truck. This dimple is the culprit. I took liquid rubber gasket material and carefully filled the dimple. It rained last night and my seat belt is bone dry. This was driving me crazy. I hope this helps. I took the rear door panel off initially and that was a waste of time. good luck and hope this helped.

 

Thank you @ktalbott, mine started leaking a while ago. The seat belt fabric on my 06 AC is discolored because of the leak. I'll give this a try.

 

This did not work, still getting wet seat belt.

 

I took a few pics of my seal.
At the very top where the 2 seals meet, they should over lap and touch/smash together.
See if yours looks different maybe?

1st pic is rear door seal
2nd is door just cracked open.
3rd is door shut all the way.
4th is the piece on the front door that over laps AND rest on the rear seal.

 

Thanks for the pics. I'll try again.