One problem related to transmission noise has been reported for the 2007 Chevrolet Avalanche. The most recently reported issues are listed below.
Transmission failed on acceleration from stop. Brought to Chevrolet dealer who told me "the 1st and 2nd gear came apart internally" and that a complete rebuild was necessary. No prior indications of transmission problems (I. E. Slipping, noise, etc. . . ). Will cost me over $3000 to repair. Searching on line, I found several other owners complaining about the same problem with less that 90000 miles on their vehicles.