Manufacturers from the beginning of time has always suggested to check ATF at normal operating temperature, car in park and engine running. I normally check this at a gas station before I fill up. Wonder how they check it at assembly plants when doing hundreds an hour. Checking in today's cars...
These sites for discussing exchanging problems and information are great. Though it becomes a guessing game as to the type of truck, age, miles, and location. So many people assume to do no maintance on it, drive it until an idiot light comes on. Then for the first time post a problem and it...
Make sure all your grounds are good, and clear the code by disconnecting the battery to see if it comes back. Here's another site talking about the same issue. 2006 Toyota Tacoma ODB II code P O 983 - Toyota Nation Forum : Toyota Car and Truck Forums
You might want to look at this thread about the Tacoma 2016 howling noise. https://www.tacomaworld.com/threads/solved-howling-noise-between-35-45.410480/page-5
Thought this was interesting on another site, a guy had a howling sound @ 50mph on his 2016. Come to find out their was some holes in his front suspension frame arms, as the air ran over the holes @ a certain speed it would howell! [SOLVED] Howling noise between 35-45
Go to another dealership to see if they can look at your problem. Keep your receipts, if they blow you off contact Toyota about it, ask if you can take it to a local front end specialists. Since the grease monkeys at Toyota don't have a clue what they're looking at.