4th gear is straight through on the KM 145 tranny - it is possible that the bearings supporting the 1,2,3,5, and reverse have failed and or the secondary shaft has sheared off, disconnecting the gears from the main shaft. I lost a tranny one time due to oil loss out the tailshaft from a half assed repair for the tailshaft seal - lost lower shaft bearings and all gears but 4th.