High and low issues...Super low works fine...Any help???

[sledhead369]

i have a 2000 suzuki king quad 300 4x4. It has super low, low and high. Super low works just fine. When i shift into low or high it wont move. There is no clunking or grinding. It feels like something is holding it back. It feels like if you were to hold the brake and hammer the gas. everything works in super low, shifts through the gears just fine, 4x4 works fine, etc. but nothing works in low or high. Any and all pointers are greately appreciated. Thanks in advance.