Daewoo DSL801 Backs up faster than it goes forword

I borrowed my DSL801 to a friend when he had it he blew a drive hose and replaced it. I noticed that it goes almost twice as fast backwards as it goes forwards. The speed it goes forward does not seam to be any slower than before. The drive motors are strong, they have about 200 hours on them. My friend is a farmer not a mechanic. Is there anything he could have done to cause this.

Daewoo DSL801 Backs up faster than it goes forword