What was found
AFTER PUSHBACK THE CREW REPORTED A -R PACK AUTO FAIL- CAUTION MESSAGE AND SMOKE IN BOTH LAVATORIES. THE AIRCRAFT WAS EVACUATED THROUGH THE MAIN CABIN DOOR AND TOWED BACK ON THE GATE. MAINTENANCE INSPECTED THE COCKPIT AND CABIN. NO EVIDENCE OF OVERHEAT/SMOKE WAS FOUND. THE RT PACK WAS VISUALLY INSPECTED. NO DEFECTS WERE NOTED. THE RT PACK WAS DEFERRED IAW MEL 21-51-01-2 CODE C, AND THE AIRCRAFT WAS RELEASED FOR SERVICE. AFTER FURTHER TROUBLESHOOTING ON 060330 MAINTENANCE FOUND THE RT PACK AIR CYCLE MACHINE IMPELLER BINDING. THE ACM WAS REPLACED WITH A SERVICEABLE UNIT. THE AIRCRAFT WAS THEN RELEASED FOR SERVICE.