I don't know. I just had my PV's M41 apart (to replace munched syncro cones) and the OD unit just slid on and off with very little problem. I put the metal collar on the transmission first, then mated the OD unit to the collar. That way you can keep an eye on the aluminum OD pump collar and make sure it doesn't tangle with the transmission shaft eccentric as it goes on. I've also heard in the past that if the OD was last disengaged under a load that it can make it hard to remove and replace the trans shaft.