I am very disappointed with John Deere's crappy K44 non-serviceable transaxle on the L120. This is the same transaxle used on many of their "home use" products.
As a result of the cheap tranaxle, the tractor began exhibiting traction issues while going up a moderate incline. Changing the oil in the transaxle helps, however, it's simply not the same as a working unit. The fix is to upgrade the K44 to a K66 at a cost of around $2,000.