PTO Problem

[Randy N]

I have an oil leak from the PTO on my M37. Closer inspection reveals that the leak is from the idler shaft. This is the one with a lock nut and a cotter pin. It appears that the shaft has been turning and there is signficant end play (maybe 1/8"). It looks like the nut has done some damage to the housing surface from turning. It also looks like someone had done some work on pto before I bought the truck as there are new seals installed.
The manual says to tighten the nut until drag is felt, then insert the cotter pin. It looks like I will have to drop the pto out to inspect and remedy, but wanted to get some thoughts here first. Has anyone had any similar issues? Is the idler shaft a sliding fit or should it be a snug fit when installing?
Thanks

[MSeriesRebuild]

I have an oil leak from the PTO on my M37. Closer inspection reveals that the leak is from the idler shaft. This is the one with a lock nut and a cotter pin. It appears that the shaft has been turning and there is signficant end play (maybe 1/8"). It looks like the nut has done some damage to the housing surface from turning. It also looks like someone had done some work on pto before I bought the truck as there are new seals installed.
The manual says to tighten the nut until drag is felt, then insert the cotter pin. It looks like I will have to drop the pto out to inspect and remedy, but wanted to get some thoughts here first. Has anyone had any similar issues? Is the idler shaft a sliding fit or should it be a snug fit when installing?
Thanks

This shaft is tapered & gets tighter the further it is pulled into the housing by the nut. If it has been spinning as you described, it's very possible that the housing bore is ruined to the point the shaft will not pull far enough to tighten. The deal is this, the bearing preload is adjusted by the shaft position, the more the nut is tightened, the more preload is applied. As I mentioned earlier, the shaft is tapered & gets tight in the housing. It's a delicate balance, shaft in housing bore getting tight at the same time bearing preload is correct. Since the shaft has spun causing wear in the housing bore, this is the source of the leak. Very likely what may happen when you tighten it now is the bearings will get too tight before the shaft will lock in the housing causing the oil leak to continue. The large shoulder on the shaft, opposite end from the threaded portion is the part that is tapered & locks the shaft, however after spinning, both ends are likely worn.

[Randy N]

Charles
You have confimred my fears. I will have to drop it out and pull it apart as I havent done that yet. I am going to see if I can machine an ocersize shaft and/or ream the large end bore as required to replicate the original design.
Thanks

[MSeriesRebuild]

Charles
You have confimred my fears. I will have to drop it out and pull it apart as I havent done that yet. I am going to see if I can machine an ocersize shaft and/or ream the large end bore as required to replicate the original design.
Thanks

Disassemble & find out exactly what has taken place first of all. Depends on housing wear as to whether an oversized shaft diameter may work. You can't oversize the shaft area where the bearings run, only the shoulder end, if the leak is at the nut end due to housing wear, the housing is trash unless you can build up the housing bore on that end & line bore to insure a perfectly straight shaft installation. By this time the repair cost will be getting up there, probably better to get a new housing, maybe even a whole new PTO.