What do you mean by "blowing out"? I had a couple thousand hours on a 60" front mount deck and never had any gear box issues, come to think of it, only changed the oil in it once! What exactly is your problem. From the sounds of it, you must have a 5000+ hr machine on your hands! Time to sell!
2004 GMC 2500HD Reg Cab BOSS 9.2 V-Plow
2013 eXmark LazerZ X-Series 60" 34hp EFI (RED) Kohler
2006 Hustler SuperZ 28EFI 60" Power Chute Design OCDC SOLD!
1996 48" SCAG Belt WB 14hp Kawasaki Classic Deck
Echo 2 strokes PB-755 & SRM 280
Eastman WM20H 20" Commercial Push mower (NEW for 2013)
Commercial Lawnboy trim mower 3-FOR SALE!http://www.lawnsite.com/showthread.php?t=424203
Solo since 1980