I have a John Deere lawn tractor,modelL120,4 1/2 yrs. Old,85 hrs. use and maintained regularly.This season it barely moves w/ or w/o blades engaged and no matter how fast engine is running.It seems as if it may be in a bind(one of the rear wheels?), but transmission doesn't appear to be slipping.Increasing throttle does not increase speed.I have pushed and pulled trans. Rod and it seems o.k. Could this be a belt problem,trans. Or brakes(although park brake is disengaged)--Any suggestions? ---Buckminster

Have you checked the brake? Already had a small john deere tractor this year that was having similar problems, and he had forgot that he set the brake last year and did not release it this year. I went to him, released the brake and all was well.