Prius 2007 shakes at 50mph or more ONLY when accelerating

Hi everyone, I have a Toyota Prius that I own since 130k miles. When I got the car I replaced the oil, of course, the coolant (It was yellow) and the transmission oil (by the way I'm so thankful for this community, everything was based on posts and tutorials from you guys ❤️). Both coolant and transmission oil I got at the dealership.

Now, with 160k, the car shakes only when I give gas. It's not the steering wheel that shake, it's the WHOLE car. Like when the back tires are not balanced. But they are (by the way, when that issue started, I replaced all 4 tires because I was planning to change in that month anyways, but it didn't changed anything).

So then the other day I lifted only the driver wheel and made the wheel to rotate at 70mph. I didn't felt vibration at all. But then I did the same with the passenger side, and I felt the exact same vibration. So then I was like... Ok... I hope it is the CV axle. I replaced that and the same issue persist

In the same day I was like... Ok, I'm done! I brought it to a mechanic. Two days later I go to get my car and the mechanic wasn't able to find the issue. I don't know where to shoot anymore. Did anyone had any similar issue before?

Ps: sorry for my bad English, it's my 3rd language.

Cheers

 

thanks for answering!

No engine lights, no misfire. Also I replaced the spark plugs 2 days ago and nothing has changed... I can hear the engine and it sounds smoothly... Also, when I'm 55mph with the engine almost off (foot off the accelerator) and i give full gas, I can feel instantly the vibration. So I guess even with the engine "off" but accelerating, it vibrates.

 

nobody after that mechanic. Should I bring it to a transmission specialist, or Toyota? (I don't know if Toyota gives free estimates)
Anyways... It shakes a lot, I can see the passenger seat shaking and it's very noticeable for passengers. ={

About shocks/struts, I'm pretty sure they're not that bad (I don't know if they're the originals), because when I'm breaking on a bumpy road, the brakes works solid... Also, no noises or continuously movement (up and down).

Cheers

 

Do you know the location of that? And, what should I expect to see? I did saw two (top engine on the passenger side, near de belt, and one right in the middle of the car under the engine), but I have no idea if they're faulty. It looks normal but I don't know what to expect, maybe I'm wrong. I will take another look and update you, thanks!!

 

The one that was in the car had, the newer one doesn't have (it's not OEM). But the problem is exactly the same, didn't changed a bit. No even 1% lol

 

I drained the trans fluid, cleaned the magnet on the bolt and filled it up (w/ a transfer pump) till transmission fluid came out of the upper bolt. That i did 30k miles ago.

Yesterday I also changed the fluid again, which by the way was a little dark (not black, but wasn't red), i put some in a napkin and it was pretty red, I guess it was in good condition. The only thing that I did different this time was vacuuming (with both bolts off) the rest of the oil, just to kinda completely drain.
But... Nothing changed. Issue persist. I will do that tests and update you. Thanks and cheers =D

 

So sorry everyone for my delay, thanks so much for answering and giving me suggestions. I replaced the driver CV axle because it was leaking (by the way I did a gigantic mess, all the brand new transmission fluid felt in about 30 seconds . I was ready for that when I replaced the passenger side, and anything happened. So I was like, ok... That's not going to happen in the driver side. DUMB!!)

My problem was fixed (of course I had to replace the transmission oil again lol). Unfortunately I didn't followed any tutorial in here, so maybe I skipped some crucial step, but everything seems to be working 100% and without any leaks.
Again, thanks for everyone trying to help, you guys are a legend!!