Yotard pretty much summed it up. It sounds normal. I would add a trans cooler and temp gauge so you know when to back off of it so you won't cook your trans.

 

I dont think this is normal. It wasn's doing this when I bought the truck or was driving on freeways.

I have a trans cooler already installed.

Does anyone think this could be the torque converter going out?

 

Looking through this post, I noticed you said you have 4.56 gears with 31" tires and an auto trans. The factory option for 31" tires and auto have the 4.88 gearing. You should have 225/75/15 tires. If you look at your plack on your door, it should say the tire size. Living in NH, I've got some nice hills, but nothing like out west. It will sometimes downshift to 3rd if I am doing 55-65ish. At 70+ no issues.

 

I hate to contradict you, but you're wrong. I have worked on many a 4runner 3.0 auto with 31's and 4.56 gears as per the placard. Believe me, I look at every plaque...dont ask why I'm weird like that

 

Now having issues with none of my windows rolling up. Anyone know where this fuse is??? Thank you!!