that snapring is the diode snapring, common failure.
Those vids were on MN12Performance for years.
I have one out of a 4X4 truck on the bench with the following.
That snap ring he is talking about is totally off and destroyed.
They 'bottomed out' the vehicle and mashed the pan into the black harness and filter breaking off pieces that wandered all through the transmission. (the real cause of death in this case)
The case was cracked in a place where the case meets up with the extension housing which wasn't visible initially and hadn't been leaking. It had been that way for a while based on the corrosion I saw when it came apart.
And, the e-clip on the OD servo is broken.
There was also one of the common 'stupid' related problems and I can't think of it for the life of me. Too damn early.
That dude is HARD on vehicles.
All of this added up to smoked ugliness internally, but the hard parts were ok. The transmisison obviously saw way too much rpm more than once and obviously had been offroad to have mashed the pan and cracked the case like that.
I am glad this was a core instead of a customer. Even though I only ended up with parts instead of a buildable transmisison, I am still better off. I wouldn't want to try to build a transmission that would have to take that abuse. I bet the rest of the truck it came out of was beat to hell too.