From the MBTA's capital budget available on their website...
Green Line No. 7 Car Midlife Overhaul
This project encompasses a number of component repair and replacement efforts for the Green Line No. 7 fleet. The scope includes replacing and adjusting the obstruction-sensing system on the car doors, modifying the wheel profile to improve rider quality and vehicle stability as well as minimize wear on the track, upgrading and repairing the coupler support rods and spherical bearings, reengineering and upgrading the brake actuators, and replacing vehicle roofs. This project is an expansion of the No 7 Fleet modification program.
Green Line No. 7 Car Midlife Overhaul
This project encompasses a number of component repair and replacement efforts for the Green Line No. 7 fleet. The scope includes replacing and adjusting the obstruction-sensing system on the car doors, modifying the wheel profile to improve rider quality and vehicle stability as well as minimize wear on the track, upgrading and repairing the coupler support rods and spherical bearings, reengineering and upgrading the brake actuators, and replacing vehicle roofs. This project is an expansion of the No 7 Fleet modification program.