Small Engines (Lawn Mowers, etc.): transmission problems with sears lawn tractor, sears craftsman lawn tractor, craftsman lawn tractor

Question
Sears Craftsman Lawn Tractor.  20.0 HP, 42” Mower Electric Start Automatic Transmission.  Model No.  917.272922

Purchased in 2002, maintained very well and well taken care of.

Recently I have noticed that the automatic transmission will not move in the same way it has moved previously.  Specifically, when I am going up a hill.  When I push the auto trans all the way forward (to increase the speed) the mower will not move, it will just sit.  If I ease up on the auto trans (for a slower speed) then the mower will start moving again.  I just started noticing this problem last week.  

I have looked up the problem in the owner’s manual and have come up with first trying to purge the transmission (which I don’t think is the problem since the trans is not new and has not been serviced), and if this did not work then to replace the motion drive belt.

Do you think replacing the motion drive belt would be the next logical step, as it could be slipping, due to wear over time?  What do you think?

Thanks for all you help.

Sincerely,

Jon

Answer
No need to purge the tranny unless it had a leak, and air entered it. My guess would be to change the drive belt. It takes very little to not see a stretched belt and give the same results. make sure you make a simple drawing to remember the belt pattern going to and from the pulleys. If this is a vari-drive type, check the vari-drive pulley in the rear at the transmission. The vari-pulley changes size according to the shift lever (If this model has one) sometimes grass and such gets between the pulleys stopping if from expanding, and contracting in size........Tom