To enhance fuel economy Chrysler released the A500/A518 overdrives in the late 80s and 90s. The units were retitled 42/48RH/RE. Computer control was limited on these models. To further improve the offering Chrysler released the RFE (Rear wheel, Fully Electronic) family of transmissions in 1999. Although the transmissions started out as four speed, they became five speeds and even six speeds in later years. The list entails 45RFE, 545RFE, 65RFE, 66RFE & 68RFE. Over the years, changes have occurred to components such as the pump, valve body and solenoid body with the most recent changes occurring in 2019. Use caution when interchanging parts.