What was found
AFTER TAKEOFF, PULLED GEAR HANDLE UP, RECEIVED "GEAR DISAGREE" RED WARNING MSSG, COMPLIED WITH QRH, RETURNED TO ATL. UPON LANDING CLEARING 27R RECEIVED "HYD3 HI TEMP" MSSG AND LOSS OF NOSE WHEEL STEERING. COMPLIED WITH QRH, TOW TEAM PULLED AIRCRAFT INTO GATE. AIRCRAFT RETURNED TO ATL AFTER TAKEOFF. EMERGENCY DECLARED.