55.2-59 58 4 speed Transmission issue

[oldironpeddler]

I have a 1958 Apache Fleetside with a 4 speed Transmission. I recently swapped out the 6 cylinder for a OM617 Mercedes Diesel. Now that everything is put back together the transmission shaft continues to turn even when it is neutral. I cannot seem to figure out what the problem is. I have the top cover off and have manually shifted thru the gears, yet the only way I can get it to stop is holding in the clutch pedal. Other than that is seems to be in gear no matter what I do. Any Ideas how to solve this? Thanks.