Transmission bucks when downshifting

2008 PreRunner at 263,XXX miles. Had the fluid drained and refilled, but noticed a ton of sluggishness to a crazy degree, had it flushed by another shop, same issue, took it to Toyota, and they said it was 4.5qts low on fluid. No idea how two shops missed the low fluid, but now I know to only let Toyota deal with trans fluid.

Started driving it and gave it some gas while doing around 50mph, I thought I hit a deep pothole. Revved it again and while shifting it SLAMS into gear and jerks the whole truck. Depending on how much gas I give it, the same happens. If I don't give it too much gas and drive it pretty normal it seems fine, almost seems like going from 5th to 4th has no issue, but when going into a lower gear and giving it more gas it hits HARD.

I plan on taking it to a transmission shop once I can get an appointment, anyone have any idea what could be causing this?

 

Post a pic of the driveshaft.

 

Will note that my drive shaft was recently Por15’d along with the frame.

 

Center bearing looks ok, I guess. Shit, I don’t know.

 

Could be electrical. I've seen transmissions do some weird stuff after mice chewed insulation off wires and they shorted. Shrink wrapping the exposed wires fixed the problem.

At 260,000 miles I wouldn't have touched the transmission. What you've spent at 3 different shops, soon to be a 4th, would have gone a long way towards having it rebuilt. Which you're probably going to end up doing anyway.