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Finish Mower/ PTO shaft question?


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#1 QAW13310 OFFLINE  

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Posted April 16, 2011 - 12:55 PM

I bought a John Deere 272 6' finish mower last fall that needed some bearings and is missing the front half off the PTO shaft. I am going to be mowing 12 acres with my '55 Ford 850.

I have the deck rebuilt and started to address the missing half PTO shaft. After about an hour at my local JD dealer, they said the half I do have is not what came with the mower new. Long story short, I bought a new complete pto shaft at TSC, with one small problem.

The mower gear case has a 1 3/8" smooth shaft, with a 5/16" keyway and a 3/8" bolt hole 90 degrees off the key. According to JD, it used a grade 5 bolt and there is no need for a sheer bolt or slip clutch, because the mower belt would provide the "slip" if something were hit.

The new pto shaft has a 1 3/8" female smooth yoke ( that fits great ) with a 1/2" hole made for a sheer bolt, and no key slot. I do not want to drill the mower gear case shaft out to 1/2", I think that would just add long term problems. Should I...

a) Get some 3/8" to 1/2" steel bushings to cut and place in the new yoke and use a grade 5 3/8" bolt with no key. Do you think the bushings would hold up without a key and the belt would provide enough slip to protect the expensive parts?

b) Use the old keyed yoke and try to find a combination u joint. Unfortunately, the new TSC shaft and the old yoke are different and would require a "special" combination u joint. I'm sure it could be done, but could be time consuming and frustrating.

c) Add a slip clutch on the mower gear case shaft that the new pto shaft would fit right on to. I'm leaning towards the slip clutch. It's the most money, would it be worth the added expense in the long run? Or is it overkill and not needed?

d) Any other suggestions I've missed?

I do already have an over run clutch on the tractor pto, since the 850 has a transmission driven PTO, so I might have to shorten up the pto shaft abit if I add a slip clutch. That's not a big deal.

The cheapest way is the 3/8" to 1/2" steel bushings, but I'm worried about it wearing and then making a mess of everything. I mow alot of ground.

I apologize for the super long post, I just wanted to be clear. Suggestions???

#2 DanO OFFLINE  

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Posted April 16, 2011 - 01:18 PM

I definitely would NOT use any set up without the Key..the collateral damage that would be caused if that belt didn't slack enough to compensate for a Hard Hit would be Ugly and Expensive. I would try my best to use the keyed yoke & u-joint combo. Once you have it all togeather it would be most dependable and easy to service if needed.

#3 QAW13310 OFFLINE  

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Posted April 16, 2011 - 05:37 PM

Dano, I agree. I want to use the key. I went to TSC looking for a new yoke that would fit the mower gear box using the key, and fit the new u joint on the shaft. I also looked at slip clutches. They had nothing that would use the key. I've spent the past few hours trying to remove the old yoke off the old pto shaft I have, and I can't get the metal protective cover off, to remove the joint. I've put ALOT of pressure on it, there has to be something I'm missing. I'm taking my camera back out, maybe if I take a few pictures someone can tell me how to get that dang cover off so I can accurately measure the ujoint. Sometimes the most simple things turn into the biggest pains!

#4 dryrun OFFLINE  

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Posted April 16, 2011 - 05:40 PM

QAW' In my opinion, a little more money spent now on a clutch that will fit your gearbox/new driveline, would be money well spent in long run. Belt will slip to protect drive line, but the overload that destroys drivelines is INSTANTANIOUS loads that the belts cannot react to. The clutch, properly adjusted will protect you, and you will have a driveline that will last a long time. I mow about 80 acres of fescue on an estate every week, I use a Case farm tractor, and a Woods 16 foot Bat Wing Bush Hog. This Woods has a clutch on all three gear boxes, and one clutch on the input shaft. If you follow manufacturers directions for adjusting and testing, they will protect your unit, and driveline. On this woods, you are talking 2 thousand dollars a copy for input shaft and yoke assys. Oh, and one more thing, don"t let anyone talk you into putting a CV joint on the pto, claiming a tighter turning radius. IT JES DONT WORK OUT. One steep ditch crossing can destroy it.

#5 QAW13310 OFFLINE  

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Posted April 16, 2011 - 06:23 PM

The John Deere dealer tells me this isn't the correct PTO shaft for this mower. Although it looks just like what John Deere - Parts Catalog shows.

The outside protective casing is 1/16" metal. All the new ones are plastic. How do I remove it? Ive put a alot of pressure on it. All I need is the yoke I can't get to. The rest will probably be scrap.

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#6 DanO OFFLINE  

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Posted April 16, 2011 - 07:16 PM

Hard to Guess without seeing it up close but It seems to me there should be some type of release Clip, Pin or Set Screw somewhere, maybe covered with Dirt not visible, that allows that shaft to be released and slip out of the caseing. the Oval opening on the shaft caseing is interesting??? Could it be there? Only other thing I can think of is that it's a two Piece shaft, possibly with oposite / left handed threads. there must be a way of looking this up in a repair manual . Obviously that Shaft Must come out to change that U-Joint. So I can't help but think the solution is "Hiding in Plain Site"

#7 tractormike OFFLINE  

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Posted April 16, 2011 - 08:26 PM

The John Deere dealer tells me this isn't the correct PTO shaft for this mower. Although it looks just like what John Deere - Parts Catalog shows.

The outside protective casing is 1/16" metal. All the new ones are plastic. How do I remove it? Ive put a alot of pressure on it. All I need is the yoke I can't get to. The rest will probably be scrap.

[ATTACH=CONFIG]13196[/ATTACH][ATTACH=CONFIG]13197[/ATTACH][ATTACH=CONFIG]13198[/ATTACH][ATTACH=CONFIG]13200[/ATTACH]


Try this to remove the steel shield. In your first picture the rectangular white plastic inserts need to be removed. The part you see will have a tail part on one side of the rectangle that slips into a groove in the PTO shaft itseld. To remove these pry up on the side without the tail and pull out the inserts one at a time. Once you have them removed the shield should be free to come off of the shaft itself.
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#8 QAW13310 OFFLINE  

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Posted April 16, 2011 - 10:57 PM

I went back to the John Deere online parts site. There is a C clip that was buried under the grease and I did eventually get the cover off. I thought I was home free. But, someone has hammered on, and mushroomed, the yoke around the u joint cap. So, I can't push the u joint caps through. Tomorrow is a new day and I've had all I can stand today. Thanks for you help!!!
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#9 dryrun OFFLINE  

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Posted April 17, 2011 - 01:12 AM

GREAT POSTS GUYS!!!!!!!! This a much neglected and overlooked area of maintainence. Driveline repair and maint. is one of those very important, and taken for granted areas of repair. Also very costly and time consuming parts wise. Our Woods batwing costs about $1700.00 to replace, if you go with standard parts. If you use the CVjoint, about 5oo.00 more. all the different manufacturers of safety guards use different methods of attachment, and your careful inspection and detective work tells me you do fine work. These are both excellent posts, and worthy of being saved, this is info you won't get from MaDEERE or anybody else. Especially the young person behind the counter who was born 20 years after this unit was built, and really has no interest in it whatsoever. Even a john Deere CV joint is $535.00, not including ujoints at $80.00 a pop. I have run copies of these posts to my documents, as a lot of people should do, for future reference.

also might add, a die grinder with a flat end burr is useful to clean out mushroom syndrome in the yokes, just a thought.

#10 coldone OFFLINE  

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Posted April 17, 2011 - 07:41 AM

Would it be possible to use the Male end from a different PTO shaft in the female JD shaft? I am going through something similar with a JD 261 mower. The snap coupling to lock the PTO shaft on the tractor is gone and JD say parts are NLA so they want me to buy a new yoke and Universal at a cost of $115.

#11 QAW13310 OFFLINE  

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Posted April 17, 2011 - 10:18 AM

Before I bought the new PTO shaft, I tried to get just the male shaft from John Deere. They said the old end I have wasn't the original shaft and they could order a Weasler 6' male shaft that I could cut down and build the rest. It's OBVIOUSLY the correct shaft that came on the mower, I found the C clip to remove the cover looking at diagrams of the 272 mower on John Deere's website!!!

I then went to TSC and they had a front half shaft that looked like it would work, but it wouldn't fit. The inside of the old shaft is 1" x 1-1/8" and the half shaft at TSC was exactly the same. I checked them both for burrs, they just wouldn't slide together. With some grinding, I'm sure I could have made it work, but that is not the right way to do things. These are machined to fit for a reason. So, I returned the new half shaft and bought the new whole shaft. Which led up to the original question I posted. Knowing what I know now, I could return the new shaft to TSC and print off the parts diagrams from John Deere's site. Go back to the dealer, don't let them look it up or even tell them what I'm working on, and tell them the part numbers I want. What I need is part number "AM38522 U-joint with shaft and shield". It is not listed as no longer available and they don't list any substitutions on the John Deere website.

But, that doesn't take care of adding a slip clutch. The deck was built in 1986, so it's made it 25 years without a slip clutch. If it's lasted this long, maybe I don't need one? With the amount of mowing I do, I do like the thought of having one, just in case.

#12 coldone OFFLINE  

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Posted April 17, 2011 - 12:57 PM

Try this link to order your parts.
John Deere Parts Superstore for John Deere Lawn Tractors, John Deere Gators, John Deere Walk Behind Mowers and all John Deere Equipment, including John Deere Accessories.

They are the ones that told me i would have to get a new yoke, but the price was cheaper than the JD dealership.

#13 ghenges OFFLINE  

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Posted October 27, 2011 - 02:39 PM

I bought a John Deere 272 6' finish mower last fall that needed some bearings and is missing the front half off the PTO shaft. I am going to be mowing 12 acres with my '55 Ford 850 ...................................... The mower gear case has a 1 3/8" smooth shaft, with a 5/16" keyway and a 3/8" bolt hole 90 degrees off the key. According to JD, it used a grade 5 bolt and there is no need for a sheer bolt or slip clutch, because the mower belt would provide the "slip" if something were hit. .............................. Add a slip clutch on the mower gear case shaft that the new pto shaft would fit right on to. I'm leaning towards the slip clutch. It's the most money, would it be worth the added expense in the long run? Or is it overkill and not needed?


In reference to a slip clutch on a John Deere model 272 finish mower:

Quite aware that a 272 finish mower should not be used as a brush hog, but I have been using the 272 on some really rough mowing.
The slip clutch on the driveshaft seems to slip quite a bit easier than before the rough mowing, but it still holds OK.

Attempting to get ahead of a possible failure of the radial slip clutch I studied the very useful John Deere online parts search site.
There are 5 separate driveshaft parts breakouts for the 272 mower, but none show a slip clutch.

The gearbox itself is a Comer unit used on later build serial numbers.
The slip clutch itself appears also to be a Comer product.
http://www.comerindu...n/safety-2m.jpg
This image is from the Comer catalog:
Comer Industries

Why this slip clutch is on this driveshaft is puzzling since the John Deere parts breakout doesn't show it anywhere (I can find).
Certainly happy the radial pin slip clutch is on my mower, however, if the 272 is used as intended on smooth turf or on obstruction free ground there is little likelihood that a catastrophic gearbox failure would occur.
The only time the clutch engages it when some obstruction locks the blades, the mower will power through some very rough stuff without the clutch engaging.

One caveat, if powering the 272 with a tractor with horsepower in excess of 25 HP, a slip clutch is a necessity.

Here is my setup:
Click photo to enlarge

RadialPinSlipClutch.jpg




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