2003 PreRunner Transmission Rumble After Driving on Freeway in 2nd

Posting this for a buddy of mine he has a 2003 Double Cab Taco PreRunner with an A340 Auto Trans, he accidentally drove it on the freeway in 2nd for a few minutes at 65MPH he is also running 33's.
I took a ride in his Tacoma yesterday and he has a significant rumble/ vibration above 35 MPH, it seems to be coming from the transmission area.
There is no loss of power and no slipping the transmission also shifts smoothly between all gears.
I drive a stick and don't know much about the A340, from the research I have done it sounds like it might be the torque converter? But I really have no clue.
Does anyone have any insight on what might have been damaged?
Thanks

 

Was it driving in redline when in 2nd and on freeway?

How bad is the rumble? Does it shake the entire truck?

 

I asked him if it red lined thinking it might be engine related, he claims it didn't redline but highway speeds in 2nd gear I would imagine would be close to redline if not on the rev limiter.
That having been said it drives fine under 35 MPH, smooth at idle and it feels powerful.
The rumble doesn't really shake the truck but its loud I would say the shaking is about as bad as a really out of balance wheel would be just louder

 

I called Toyota and they said it is normal.

 

Yeah its probably just their terrain response system.
Anyway I guess my friends truck is f**ked but its a good excuse to convert to 4x4!

 

If my memory of the owner's manual serves me correctly, on a stock truck, redline in second gear on an auto yields 72 mph. If he has stock gearing with 33's, I'd imagine 65 mph in second would be several hundred rpm's below redline. Sounds like it needs to have some process of elimination type diagnosis. Rev standing still. 35 mph the. Shift into neutral. Etc...