Saw the gearstick just below the threated part and save that part for later. Then saw again something like 30mm off the stick. You cant take it much shorter because the stick starts to widen. Now weld the threaded part back and file the welder lumps and crap off. Dont ruin threads. Then just put gearstick knob back. If you did everything right the joint should sit inside of knob. No need for making more thread. Takes 10mins.