I don't have a manual. Any advice on what could be wrong? maybe a turning clutch? How tough is it to repair this? thanks.
Can't say for sure it's your problem, but the D20 series Komatsu have a dry steering clutch housing and were notorious for steering clutch disks sticking and no amount of finagling, swearing, cursing, or laying on of hands will pop them loose. Typically involves removing steering clutch to repair. Check your linkages first.