Hi, I recently purchased a '94 300tdi comercial landrover defender, which has a problem with its gearbox.When you change gears, especially first and second, you feel a kick or jerk through the clutch and hear a clunk. A mechanic told me that there was a gear in the gearbox that restricts oil flow in the box and that to remedy the problem the gearbox would have to be taken out and the gear replaced with a special drilled gear. Has anyone come across this problem before and if so, would i be better off buying a re-conditioned gearbox and fitting that or should i just replace the relevant gear.Any help or advice would be welcomed.Thx