#1R. Reverse Alto Red Eagle Power Pack clutch set for 1980 to 1990 AOD transmissions with cast iron reverse drums. This Power Pack provides more friction surface for torque enhancement, better heat dissipation for longer clutch pack life. It allows for 4 plates to fit in the 3 plate drum and 5 plates to fit into the 4 plate drum. The 3 plate drum in satisfactory condition is more available than a good 4 plate drum. With this Power Pack you can now use the 3 plate drum with confidence.