My honda model HRR2162tda serial # MZGG-7070845, self propels slowly, it almost needs a push to get going. I pulled the drive cover underneath and I could see the speed control casing was split. The cable inside is very thick, multi stranded. It disappears into the transmission. I'm not sure if the cable is bad or if the transmission itself is bad. There does not appear to be any tension adjuster on the cable. How can I figure out what is wrong with it?