AT-122 AUTOMATIC TRANSMISSION — Installation of Component Parts (e) Coat a new O-ring with ATF and install it on No. 2 piston. (f) Install No. 1 piston with reaction sleeve onto No. 2 piston. (g) Align the teeth of No. 2 piston into the proper grooves. (h) Using SST, install the new O-ring and install the No. 2 and No. 1 first and reverse brake pistons into the transmission case. (i) Place the piston return spring onto No. 2 piston. (j) Set SST as shown, and compress the return spring with SST. SST 09350-30020 (09350-07050) (k) Install the snap ring with a screwdriver. Be sure the end gap of the snap ring is not aligned with the spring retainer claw. 3. CHECK FIRST AND REVERSE BRAKE PISTONS MOVING Make sure the first and reverse brake pistons move smoothly when applying and releasing the compressed air into the transmission case.