2007-2008 Yamaha YFM700 Grizzly Factory Service Manual, Page 314Get this manual
TROUBLESHOOTING
cA slight "thunk" evident at low speed operationThis noise must be distinguished from normal vehicle operationDiagnosis: Possible broken gear teethWARNING
Stop riding immediately if broken gear teeth are suspectedThis condition could result in the shaft drive assembly locking up, causing loss of control of the vehicle and possible injury to the riderLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLL
2Check: drained oil Drained oil shows large amounts of metal particles Check the bearing for seizureNOTE: small amount of metal particles in the oil is normal_