I am a bit confused and would like some clarification of your mower malfuntion. My mower does not want to go up hill and goes in reverse very slow. Is this the tractor drive belt? Does this model L120 call for hydraulic fluid? Would appreciate any advice. Thanks,
Jen

Hi,
It could be the belt or the transaxle. Tuff Torq(Kanzaki) offers an upgrade kit for both the pump and the motor for the adventurous. It has larger pistons and tighter tolerances. There are some videos on YouTube about the job. See:
Part 1 - K46 hydrostatic drive Removal - YouTube
And:
http://www.youtube.com/watch?v=pL0B_1pqADo
And:
How to Upgrade John Deere L-Series to K66 transmission - Part 1 - YouTube
And:
How to Upgrade John Deere L-Series to K66 transmission - Part 2 - YouTube
Peace,
Clarke

Does the fact that the mower runs fine for about and hour at a time help to diagnose the problem? Thanks for your input:)

Hi,
Yes, the transaxle gets weaker when it warms to operating temperature. There is a plug in the top of the transaxle that can be carefully pried ou and a measurement taken to the top of the fluid level which should be about 30mm or 1 1/4"
Peace,
Clarke