1991 champion 740 Grader feels clutch sliping or something else please help asap

1991 champion 740 feels clutch slipping. I am new to graders this is first grader I bought in my life. It shifts all forward 8 gears but after shifting to higher gears rpm's goes higher feels cluch slipping and it is not moving as it needs to be. Up to 7 gears it is bit fine going on but if I shift 8 it seems no power even on minor hill if it have down hill there is no problem

If there is any equipment mechanic or any handyman here in Edmonton we have most of tools just contact me asap because I need this thing please email me

if anyone repair service and parts manual please email jp_trucking@live.ca

Thanks

1991 champion 740 Grader feels clutch sliping or something else please help asap