There are a total of 4 clutch packs in your transmission and hold about 20 friction plates in total, If they were slipping or worn out, then you would have high rpm with less drive, which is the opposite of what you have - you have no engine torque to spin the transmission. I dont understand that you say it works when moving, Have you not driven a proper diesel LC?? It should tear off its rear tires.Without the engine in good tune the transmission cannot work at all, Low fuel supply to the diesel pump caused by a dirty fuel filter or a bad vane pump inside the IP will cause a great loss of power, Also note that if the internal pressure of the pump is messed up by the return banjo bolt it will also show the same problems as low fuel. For testing you can get a cheap inline fuel pump and make it feed the IP - also ensure that the pump timing is correct, all nozzles spraying at exact same pressure (depends on the engine type), the engine is atleast at 90*C temperature (half gauge) - a cold diesel engine will not make any power, the EGR is not stuck open or corroded (block it off completely) and the valve clearances (tappets) are at correct clearance.