Do you think this is a transmission replacement or wiring or not a?

Question

Hi I have mechanic book knowledge but didn't get to work on cars during my schooling cause it was in prison but I know the basics. That being said I have worked on my vehicles by watching YouTube videos and reading repair flows. Okay that's so you get a sense of what I might be able to understand cause I really need help.
So I have a 2008 Nissan Altima 2.5l qr25de 2488cc engine. About a month ago there started an issue where the car would start shaking a little when you stopped my brakes were going bad I chalked it up to uneven wear but as about a week went by the shake turned to vibration then heavy vibration then all out shuddering and jerking this would have not under speed or at higher speeds but at speeds under ten miles an hour and is worse when you are coming to a stop (after you get under five or ten mph) and when you are taking off same speed considerations if i brake fast or hard not much of an issue if i take off or hard accelerate not much of an issue. But now the car which I only drive in extreme emergency less than a quarter mile to take kids to school if ride doesn't show is so much worse the engine rocks hard it feels like it's bouncing around in the front of the car you can feel it jerking the entire car but I don't feel it at all in the steering wheel or the pedals gas or braking. The shifting feels slow or doesn't seem to engage revving at 4or so rpms until I let off the gas a bit but the shifting is still smooth as in you don't feel any jerking when it upshifts or downshifts the only way to keep the ability to accelerate is to not stop at stop completely and then i only het a couple turns or accelerations before it goes into what im guessing is limp mode because it loses all acceleration but the cars owñ power and the gas pedal does nothin.
Those are the symptoms.
What I know:
It's not the brakes unless its the abs and I don't have a light or dtc for that
It does have a p1715 and a p0868 ( checked trans fluid and it was in hash to top almost don't have camera or tools to check cvt belt
I had a mechanic check with the little time he had for free he got under car put his hand on a part under the car on or near the transmission and moved the right front wheel back and forth and you could hear and he could feel a thudding sound like there was too much play somewhere but he felt it in his hand not sure exactly what he was touching but he had to remove some cover to touch it about a 3 to four inch square cover
The engine mounts are bad but I replaced the top torque mount which was completely gone not supporting at all but the engine mounts have been failing for sometime but the others are loose or giving much play as the engine when put into gear and under braked rpms only moves slightly after the torque mount replacement and the car still shook exactly the same
The serpentine belt is very thin I don't know if this would cause shuddering because of slippage but I wouldn't think it would be so violent if so
I'll be checking fuses tonight because of the codes I'm thinking maybe some power or info isn't getting transmitted somewhere
There are no knocks or grinding or scraping sounds while drive faster than five or ten mph
There is a triangle with an exclamation mark inside light on the dash and sometimes a little white light that appears to be a gauge picture
It does the same in reverse and drive
In limp mode will only go as fast as putting the car in gear and no pushing the gas

That's all I know in the clearest way I could explain it any help at all would be greatly appreciated even articles video or tech manuals I understand most flow charts and love to read new information so anything helps. Thank you for reading all this and thanks in advance for having a great community here you're appreciated.

Answer 1

Unfortunately, I haven't personally encountered that issue before. However, after checking a National Database for repairs on the same model, year, and symptoms, it seems likely that the codes indicate a transmission problem. Most shops resolved the problem by replacing the transmission. My recommendation is to overhaul or replace the transmission. The issue doesn't seem related to the engine since you would typically feel that in the steering wheel. Similarly, problems with brakes or suspension would manifest in sensations on the steering wheel and pedals.