If fluid is leaking from around the automatic transmission pan, what should be replaced?

When fluid is leaking from around the automatic transmission pan, replacing the gasket is the correct course of action. The transmission pan gasket serves as a seal between the pan and the transmission case, preventing fluid from escaping. Over time, gaskets can degrade due to heat, wear, or improper installation, leading to leaks. By replacing the gasket, you can restore the integrity of the sealing surface, which helps to contain the transmission fluid within the pan and ensures the transmission operates correctly.

Replacing only the fluid would not address the root cause of the leak, which is the compromised gasket. The rear seal pertains to the interface between the transmission and the driveshaft, which is separate from the pan, making its replacement unnecessary in this context. Replacing the entire transmission would be an excessive measure when the issue can be resolved by simply replacing the gasket. Thus, addressing the gasket is the most appropriate and effective solution to stop the leak.