A B737-300 WAS DISPATCHED WITH THE #3 MAIN GEAR WHEEL AND TIRE ASSEMBLY INSTALLED IMPROPERLY WITH B737-200 WHEEL BEARINGS RESULTING IN LOSS OF THE WHEEL.

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ACFT DEPARTED AND LOST #3 MAIN WHEEL ASSEMBLY. WAS FOUND MISSING BY NEXT FLC DESIGNATED TO FLY ACFT. WHEEL WAS INSTALLED JAN/XA/99; AT ZZZ. WHEEL WAS BUILT UP AT ZZZ TIRE SHOP JAN/XX/99. OUTBOARD BEARING (OUTER ON WHEEL) WAS FAILED. ALSO AXLE ON LNDG GEAR FOUND CRACKED. WHEEL ASSEMBLY BUILT UP BY 1 MAN; INCLUDING INFLATION; BEARING INSTALLATION AND FINAL SIGN OFF. UNKNOWN WHO INSPECTED BEARINGS AS NO PAPERWORK COVERS THIS. 1 MAN SIGN OFF STANDARD PROC IN THIS TIRE SHOP. MECH RECEIVED NO TRAINING FOR TIRE BUILD-UP. BEARING STOCK IN SHOP NOT CTLED. NO SECOND EYE SIGN OFF FOR BEARING INSTALLATION OR BUILD-UP. UNKNOWN AT THIS TIME EXACT CAUSE OF FAILURE. MECH WORKS PART TIME IN TIRE SHOP. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE B737-300 WHEEL AND TIRE ASSEMBLY WAS BUILT UP IN THE TIRE SHOP IN ZZZ AND INSTALLED ON A B737-300 ACFT IN ZZZ. THE RPTR SAID THE TIRE AND WHEEL ASSEMBLY WAS BUILT UP CORRECTLY EXCEPT IT WAS DELIVERED WITH A B737-200 WHEEL BEARINGS WHICH WERE INSTALLED CAUSING THE OUTER BEARING TO FAIL; THE WHEEL DEPARTING THE ACFT AND THE AXLE INCURRING DAMAGE. THE RPTR STATED THE PERSON WHO BUILT THE TIRE AND WHEEL ASSEMBLY AND MATCHED THE IMPROPER BEARINGS TO THE ASSEMBLY IS NOT REGULARLY ASSIGNED TO THE TIRE SHOP BUT WAS SENT IN TO HELP DURING A BUSY PERIOD. THE RPTR SAID A BETTER METHOD OF SIGNING OFF JOB CARDS AND INSPECTION PROC IS NEEDED.