'47 Cub PTO shifter

I have a "47 Farmall Cub whose primary duty is to run a Woods 5 ft. belly mower. For the past decade or so she"s been our regular (and only) mower. Late last fall the PTO threw itself out; upon dissasembly I found the shift lever ground nearly off where it goes into the PTO shaft shift collar. Replaced shift lever but it was too late in the season to run her again.

Spring has come early here in NW Penna. (as it probably has in most of the country) so time to cut grass once again. The poor Cub only made it about three minutes before the PTO threw out again and sure enough the brand new shift lever is ground off same as last fall.

I doubt lubrication is the issue as the trans. is full of fresh GL-4 SAE 90; even if inadequate oil were in there, 3 min. to failure???

There is no visible wear in the groove of the shift collar. Collar fits on PTO shaft without abnormal wiggle. PTO shaft splines look straight, no shaving of the points. Trans. output shaft splines are straight except for the last 1/16" or so where the leading edge is tapered very slightly in; the OD of the splines is uniform throughout their length however. I"m not sure if this taper is factory spec. or due to wear but it appears minor. There is negligible end play of the PTO shaft in its bearing and there appears to be no end play on the trans. output shaft; no lateral freedom of movement on either shaft. Collar was replaced with new shift lever and internal splines still look brand new (old collar looks fine too, but replaced just incase.) With collar removed and PTO shaft inserted into trans. shaft there is a good 1/4" maybe more of distance between the body of the two shafts -- not sure what spec is.

Questions -- What the heck do I do? I would think the two shafts would run tighter together than they do. the collar can only grab 1/4 inch or so of the trans shaft splines I would think, but if this isn"t spec then how did the shafts move? surely something is forcing the collar rearward from the engaged position to the released position and that poor little shift lever just can"t resist for long ... but what?

Thanks in advance,

Pete P.
Harborcreek, Penna.

With the PTO shaft and rear plate removed, grab ahold of the transmission shaft and see if you can pull it front to back. Also, how much does it grind when you put it in gear, either transmission or the PTO?

I"ll try testing end play again with dry hands, but with oily fingers I couldn"t get it to move.

Trans. works fine, stays in and no grinding. PTO stayed in fine for the three minutes, then the collar was able to move off the trans. splines and ground like heck.

Pete P.
Harborcreek, Penna.

There are a couple things that haven't been mentioned in this thread that you probably should check.

- Transmission shaft is held back by the transmission front bearing seal retainer. If the retainer is installed backward (unlikely this situation), the shaft can move forward. A failing bearing could cause the same. Either way, this should show as end play in the shaft.

- PTO shaft held forward by its bearing. The shaft could have moved back in the bearing. This probably would not show as end play. Inspect the shaft (outside the housing) to see if more is exposed than before. In '47, the shaft was staked to hold the bearing. Later a snap ring was added.

- There is a pilot bushing in the back end of the transmission shaft to support the front of the PTO shaft. Check it for wear. If the two shafts aren't held in strict alignment, it will generate force that tries to disengage the PTO.

Thanks for the ideas. I've owned the tractor for more than ten years and never had reason to go into the transmission itself so I'm skeptical about the bearing retainer. I have replaced the PTO bearing now that you mention it; I staked it on as you mention -- I wonder if my staking job let go?

I think I'll pull the PTO bearing back apart and re-stake, renew the pilot bushing and see if I'm lucky.

Has anyone fabricated a longer collar that would grab more of the trans. shaft splines but still be able to release fully? I'm tempted to weld two collars together using a junk shaft to align the splines & hold the units to a true center, then cut off the 'extra' shifter lever groove to make the length as long as possible.

I'm worried that somehow the splines on the trans. shaft have worn in such a way that they're acting like a Bendix on a starter, trying to throw the collar rearward. They don't look worn, but removing that shaft looks like a big pain.

Wish me luck & thanks,

Pete P.
Harborcreek, Penna.