Hello,
I am just trying to get some help on determining what my problem is before I head to the mechanic (since I don't trust them for the most part). I feel a slight knocking when I turn and brake. Today I got under the 4Runner and could feel an obvious movement, I put video below...any help is appreciated. https://youtu.be/dIg45wtIc10

The cv joint looks tight, but the whole cage rocks in the case.
Are you sure it's snapped all the way in?

I just purchased a 2016 july . I did a pretty good inspection under over most all the vehicle .. your front diff axle movement is what I have at 400 miles. now on my 2000 GM silverado 4WD 170K miles there is no movement .

is this normal ? I was going to bring it in myself both side move IMO too much.

Looks like the needle bearings are shot. It's a design flaw by Toyota in the carrier IMHO. Usually causes a vibration in the diff.

There are possible fixes. Search google for Toyota clam shell stub shaft bushing....

I don't know what "normal" play is. My front diff has an ARB carrier and there is 0 play on both sides. But that is comparing apples and oranges.

is there a fix for this issue?

like replacing the needle bearing with this?

this is the first time i have heard of this. I have a 2010 and dont have the issues the OP describes, but that doesn't mean i wont ever.

The issue I'm talking about is sort of hit or miss, I think. Toyota uses a cast design where the spider gear sits in the carrier (no machining). So there is some play and this puts some additional load on the sub shaft bearing. They can wear out fast depending on how accurate the cast was.

The typical symptom is a roar/vibration/noise from the left side CV. A lift will definitely exacerbate the issue, but it can also happen with stock ride height.

It was a huge problem on Tacomas for a while, but has not been talked about much for 5th gens...So IDK how common it is or if it will be as they age. It is the same diff and carrier. Maybe they revised the casting process at some point... not sure

This video explains the details. The solution is replacing the needle bearings with a bushing that provides a better fit with less wear.