I drive a 92 civic lx with a auto trans it has about 200000 miles on it and as I was driving home yesterday my car kept going into neutral so I limped it home found out the trans fluid was burnt so I changed it out and now I can manually shift the gears while driving but it won’t go above 45mph and when the car is in reverse it shakes and barely moves. And finally when I put it in park after driving it makes a short grinding noise like half a second long. Also the check engine light isn’t throwing any codes

 

Doesn't sound good.

Start by checking the shift cable adjustment.

What ATF did you add to the transmission?

Also try 3-5 additional ATF drain-refill cycles. After each drain-refill, SLOWLY move the shifter through all of the gears multiple times with engine idling to maximize ATF circulation through the transmission.

Good luck.