MOPED ARMY

shaking in a transmission is caused by any number of thins;

bad clutch shoe/s

clutch not aligned properly

bad clutch spring

clutch frozen or sticking to the shaft

worn clutch shoe/s

improperly shimmed clutch drum

improperly shimmed gears

improperly shimmed gear or clutch shaft

loose bolts or clips holding parts together

improper fluid level

improper fluid

worn gears or shafts

lubrication problem/s

or just plain not assembled correctly