I just bought a 2003 Mustang with a 3.8L V6 and automatic transmission. The car
runs great except for hard shifting between first and second. The car dealer agreed to install a new valve body to correct the shifting issue. The mechanic found that the car had a shift kit installed which explains the firm shifting. The new valve body was installed and the shift between first and second was smooth. However, shifting between second and third and third and overdrive the transmission slips. The dealer is going to reinstall the shift kit to see if the problem goes away. My question is - If the slippage goes away with the shift kit is everthing okay? The car has 65,000 miles and has been well cared for. I am the second owner.