Hey Scotty,
I have a 2013 chevy sonic lt sedan automatic with 123k miles on it. I received this car thirdhand recently from a family member who did not change the ATF since buying it used at 40k miles. As of recently, the car makes a thump and shake when I put the car into reverse. There has been very slight slipping of the car but besides that, the transmission responds adequately. I am planning to get the ATF replaced as soon as possible to correct this issue. I wanted to ask the following: will changing the ATF at this mileage cause more harm or should I go ahead and do it anyway (not sure if Lucas slip fix would help this issue)? I'd appreciate any advice on this situation, thanks.
Maybe change the transmission fluid first. See if that helps.
Drain and fill only. Don't flush.
If you're taking it to a mechanic for the fluid change, just ask them to check if something's loose or broken.
