niccar2021

Hi I recently just bought a hotrod off of my uncle it has a 350 small block and a TH350 trans I recently just came across an issue where it won’t shift from 1st to 2nd until the last second and when it finally does shift it shifts so hard the back tires chirp...it shifts normally from 2nd to 3rd and does not slip at all. I just changed the fluid and filter and it still shifts like that...some people that I talked to said it could have a shift kit and that’s why it shifts so hard and others say the trans is going out...my uncle said he didn’t know if it had a shift kit or not. Does anyone know what’s up with it?