Take a look at the 2/4 drive switch for power .Than look at the 2/4 drive valve.To see if the valve is switching .You can check by seeing if the valve gets magnetic field with a screwdriver by feeling for a magnetic pull on stem .If you need manual with schematic please post your email address.
Go to JLG.com. They have all their manuals online. Go to resources. Then click on manuals. Then just select the brand.