you will need to take out centre gearbox tunnel cover for access.gear lever may be worn and left selector in gear, make sure selectors are inline in this position there should be no drive.if still faulty you will need to take gearbox top off [watch out for springs and balls on selectors] then selectors can be removed and checked. you may find that the plates on 3/4th synchroniser are broken/jammed,these can be changed in situ
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