What was found
ON CLIMB OUT THE CABIN RATE WAS CLIMBING HIGHER THAN NORMAL DUE TO SINGLE PACK. THE RATE STARTED TO DECREASE AND ACT NORMAL THEN WE RECEIVED A CABIN ALT CAUTION MESSAGE. WE EXECUTED AN EMERGENCY DESCENT. THE MASKS WERE NOT DEPLOYED. WE COMPLIED WITH THE QRH AND PEFORMED A MANUAL PRESSURIZATION PROCEDURE. FLT 5974. REMOVED AND REPLACED RT 10TH STAGE PRSOV AND THE RT PACK LOWER DISCHARGE DUCT IN AFT EQUIPMENT BAY IAW AMM. PERFORMED OPS CHECK OF PRESSURIZATION SYSTEM IAW AMM. ALL OPS AND LEAK CHECKS GOOD.