My 4runner V8 done this a good while as I stated and no codes at all ever showed up.
After assuming my shift issue was more likely a "nature of the beast" issue and living with it, it then got even worse so I was getting worried.
Then the other day I was leaving my friends house and I nailed it hard from a dead stop and it stumbled some, then took off. I tried it again and same thing?
I came home and popped the hood and looked at air filter, checking fuel rail,electrical plugs etc.. and double checking to see anything the squirrel I killed a few days before that climbed up under hood and without me knowing I started 4runner, biff, bang, boom (I saw center hood flex) but no damage done to truck, poor guy.

So I pulled my Mass airflow sensor out and it looked ok but I had never cleaned it once. I also saw my throttle body needed cleaned again some, it had been awhile so the next day I went and got a can of Seafoam "SPRAY" with curved tube that inserts into throttle body (see link) and a can of Mass Airflow cleaner and went to town cleaning both up.

After I put it back together and drove it a few days now it's like a new truck. It was running better immediately too btw. I had no idea how bad it really was, but after a week now it has never once hard shifted again. In fact it shifts absolutely perfect both up/down like it done before.

So it's my belief that my big balls should be held every night..Whoops!!!
Oh' sorry guys a rock n roll flashback hit me while typing..
I meant to type:
It's my belief it was my Mass airflow sensor being dirty and the slight hesitation interrupted the shift points as they must correspond together. I only wish I had just cleaned the MAF sensor first and drove it a bit to be sure but I think that is what caused most of it. TB was not that bad and was removed & cleaned before while problem existed so try MAF first.

I don't know yet if fuel milage will change I felt I needed to let its computer settle in a bit before checking that, but it sure drives sooo much better and my nerves sure settled down now knowing it's not a tranny issue so again we'll leave that up to Bruce Jenner...lol

Advice:
Don't use anything but Mass airflow sensor cleaner to clean the sensor as most carb cleaners may damage or leave a film behind. Cost just a few bucks for someone to avoid a future headache is all I'm saying here.

How to clean MAF sensor video. (I don't know him I typed into youtube search and clicked.)
https://www.youtube.com/watch?v=gRfaPfTcfOM

Sea foam says don't spray sea foam into MAF sensor, insert tube somewhere between the sensor & TB but best directly into front of TB.
Sea Foam "Spray" video if not removing TB to clean:
https://www.youtube.com/watch?v=u6UeJXkzDW8

Hope the fix for others here is as simple...Best of luck and a big thank you to everyone "again"!! Until next time...OMG! There will surely be a next time too..
Peace!


*

LOL - but should they be held for charity or fancy dress?

What ended up being the problem?? Transmission or Driveshaft? My dad's V8 4runner does the same thing. The dealer can't duplicate the problem.
Occasionally downshifts hard and loud when coming off the interstate and slowing down then getting back on the gas.

Mine has been doing this. The truck is pretty new to me and obviously it is a bit unnerving as it seems like a transmission issue, though on the electrical side of things. If I brake hard to a stop, or brake hard while driving, and then step on the gas, tre transmission hunts for gears and revs as if I’m neutral, and then bucks forward. Definitely curious if there are any modules (tps, etc) that could not be communicating properly with the trans as it simply seems to not be sure which gear to engage after hard braking.!

Have you had the transmission fluid level checked, this is one of the most common causes of a trans slipping and with these sealed trans no one ever has the fluid level checked??

Yes did the drain/refill with a new filter. Odd thing... replaced a cracked vacuum hose and cleaned the throttle body (it was bad) and the problem has subsided a lot. Kind of crazy, but I think the trans wasn’t sure what to do at stops as it was still swing some throttle. I actually did manage to find another post of someone experiencing a similar problem (with a similar solution).

Bumping this thread...

I had the same thing happen several times. Got a transmission fluid flush after the last time and it solved the shifting issues, but after the last time it got stuck in 2nd, I was on a bridge going 65-70 mph and couldn't get off for ~3 miles and now there's a disconcerting sound coming from under the hood.

Anyone else experience this and have any insights?