Q: Rough shift from 1st to 2nd.

Transmission problems can be confounding mostly because the components are so inaccessible and there are so many of them. Although the transmission is generally thought to be the most complex "component" in a motor vehicle, in principle, it actually is pretty simple. In the transmission, sensors measuring speed and engine load actuate "shift change solenoids" and other valves (all in a large valve body bolted into the transmission) which redirect high pressure hydraulic fluid to pistons that force clutches to actuate.

First thing to check is the fluid level. If the fluid level is not correct (high or low), the hydraulics will not preform properly. If the fluid hasn’t been replaced, there is a small chance that merely changing the fluid and the filter could improve the situation. If the filter is clogged, hydraulic pressures will be insufficient and can lead to delayed shifts. If fluid isn’t the issue, it’s likely that problem is the valve body (a faulty solenoid or a sticky valve), a damaged o-ring hydraulic seal in the transmission, or damaged piston.

In this case, rebuilding the transmission can possibly result in a better unit than what was originally supplied in the vehicle for the simple reason that since 2002, the parts like accumulators and valve body parts, have been re-engineered to solve all the known issues that have since been observed in the field. Before seeking out mechanic specialists to rebuild the transmission, I recommend having the vehicle diagnosed because a full transmission rebuild may not be necessary.