2005 DC trans shift noise from firewall area?

Hi There, I'm new to the forum and just getting familiar with my Tundra. Recently I had the transmission fluid dumped and replaced at Toyota dealership. Before that I noticed lazy shifts between 2 and 3rd. Or 3 and 4th? Seems to be shifting fine now, except..
Now I hear this hissing noise from inside the engine bay, drivers side happens just before shift point. Sounds like someone going pssshhhhhhhtttt then shifts. Best I can describe it. Really noticeable when the window is down, particularly between 1/2 and 2/3. Really don't have a clue where to start diagnosing on this one. ?? Thanks!!

 

Start checking for loose or disconnected hoses. Your year has the air injection thingys which may be a cause. Someone with your year Tundra will come along and help.

 

cool golden hands! lol thanks for the clue about air injection thingies. I'll go poke around this aft.

 

Well nothing obvious. But the sound is more like an electronic sound bzzzzzttt almost like a strangled duck. It’s pretty bizarre , I really don’t have any useful knowledge of computer controlled transmission like this. This noise comes on a few seconds before the trans shifts to next gear.

 

Can you get a video of it?

 

This mission shall now be called Operation Bbzzzzztttt!

Not sure if this was coincidence or now, but today I heard an old looking 4Runner (not sure year/gen etc as they’ve never really blown my skirt up) driving down the road at about 40-45 mph and it sounded like a mechanical Bbzzzzzztttt for at least 3 seconds. I was standing there thinking about this thread.