Transmission Fluid replacement at 120k?

Tacoma doesn't offer AWD, it is 4wd or 4X4. There is a huge difference and if you don't understand that you could be doing serious damage to the 4X4 components.

If your transmission is in good condition changing the fluid won't hurt a thing. Probably won't help either. If your transmission is already starting to go bad changing the fluid at this point will cause it to completely fail within a few hundred miles. If it is going bad leaving the old fluid in there will buy you some time. It may well keep working for another year or 2.

Since you have no way of knowing what the internals look like without taking the transmission apart most shops won't touch it at this point. They don't like having to explain to customers why their transmission died a week after the fluid was changed. The local transmission shop advises customers to change every 30,000 or leave it alone until it dies.

I've been driving almost 50 years and have never changed the fluid on any vehicle I've ever owned. The only transmission issues I've had were electrical. There is nearly 1/2 million combined miles on the 3 vehicles in my driveway, all with factory transmission fluid in them. If the transmission dies tomorrow on one of them, I'll have a new one installed. I'm WAY ahead financially with the money saved by not changing the fluid for the last 50 years.

As long as you never let the transmission overheat getting 400,000+ miles out of one with the factory fluid isn't unusual at all with a Tacoma. Some other manufacturers transmissions won't last 130,000 miles even if you do change the fluid religiously. Let it get too hot or buy a vehicle with known transmission issues and you'll get early failure.

 

I did two complete flushes. At 80,000 and 220,000. Blackstone results oil was in very good condition.

 

Flushes and fluid changes isn’t what hurts a transmission.
Improper flushes and a lack of modifiers is what hurts transmissions.

If a flush and/or fluid change is done properly, no damage will be done.
If you experience issues after, you already had a problem. You just didn’t know it.

My vote is drain and fill at a minimum.
Next would be drain, fill, replace filter.
Best would be a flush (done correctly)

 

I had the dealer do a full flush at 115k and helped the shifts and the torque converter lock up.
I tow and do a lot of slow heavy offroad in hot climates. Yes, many say don't do and trans may be fine - or not.
Dealers have factory approved equipment and method. New fluid can only help.