How do you replace the drive belt on a greenfield ride on mower model tractor 8?

remove the two (2) bolts holding the seat in position, these bolt also hold the rear wheel cover on, remove the seat and the rear wheel cover, pull the wheel cover slightly up and back at the same time.

If the old belt is still in place look carefully at how it is twisted and turned over each of the pulleys from automatic tension pulley at one end to the motor pulley at the other end. Note that the tension pulley has a very strong spring and a steel leaf that holds it from coming back, this needs to be released or pressed down, if you have the proper tool use this to take the tension off the pulley while you remove or fit the new belt, if you don't have the tool a length of coat-hanger wire will help do the job. It is not a very difficult job for the average home handy man to do. It can be done with the cutting deck still on the mower. It is a little bit of a fiddle at times but can be done, start to finish, in about 40 minutes if you take your time and think as you fit and trace the path of the belt over each pulley. NOTE: WATCH YOUR FINGERS AS YOU ROLL THE BELT OVER THE LAST PULLEY ! I recommend fitting all the pulleys and leaving one of the the Clutch pulleys as the last to fit the belt on as it is the biggest and by turning the rear wheels by hand you can get the belt to roll on.

I am a home handy man, I have had my tractor 8 for about 6 years and have successfully changed many drive and cutter belts in that time, it is NOT as difficult as it first appears, give it a go, if all else fails take it to the mower shop, what have you got to lose. Hope this helps in some way, cheers, Reg ;)