My Cub Backhoe's PTO shaft

Sun Sep 06, 2009 11:04 pm

I dropped my backhoe at a friend's place about 3 weeks ago, so he could use it to dig a trench-When I saw him about a week ago, I asked how it went, and if he was done with it-he said it had worked just fine, then hesitated and told me that it was having problems. I asked what kind of problems, and he said that the day after he finished the trench, he went to move the backhoe, and when he engaged the hydraulics, and started to lift the boom, it made a funny noise, didn’t seem to work as well as it used to, and on further investigation, it was spitting bits of metal out of the area of the PTO and the chain drive for the hydraulic pump.

I wasn't too worried until he also told me that a mutual friend had looked at it, and couldn’t figure out what the problem was. The guy who looked at the tractor can pretty much fix anything, without hardly thinking about it, so then I got worried...


I went over there today(and brought some come-alongs just in case) to see what was up, and if I could fix it or needed to bring it home for repairs.

Well, I took a close look at the situation, and discovered that the teeth on the PTO sprocket were all sheared off(that must have been the “spitting metal” source). I also found that it still worked, sort of-we needed to use the come along to raise the main boom, with what little help the hydraulics could give as the sprocket spun inside the chain.

Anyway-I knew teh chain was on the loose side(it had no tensioner, and I suspect it had been lubricated rarely, if at all, before I got it-so I guess the sequence of events was as follows:

The chain was only very infrequently lubricated.

This caused it to stretch.

The stretched chain was causing undue wear on the sprocket teeth, especially near the tips as the stretching caused it to move in and out and rub on the teeth

Eventually, it got long enough, and the teeth got worn enough, that the chain occasionally skipped a tooth.

Then the tips started to get rounded over, and the inevitable happened.


I took it all apart today to figure out what parts I need to get to replace things, and while doing so, I finally got to take the sprocket off of the PTO shaft-when I tried in the past, using a puller, it would not budge. The sprocket was a homemade double-row #50-2 chain sprocket, with only one accessible setscrew, but another setscrew hole in the hub peeking out from under one of teh chainrings. It looked as if someone cobbled it together from some of the "weld-on" sprockets and hubs, but highly modified. I figured maybe there was another setscrew in that hole under the chainring, but after I put the thing in my hydraulic press, it pressed right off. No additional setscrew, just some rust holding it on.


Anyway, I found that the PTO shaft has a 1" diameter, with a groove for a 1/4" key. I can;lt see any evidence of how it was modified, but I guess it must have been welded up and turned to diameter on a lathe. Here's what it looks like:
Image
I just thought some of you might be interested.

Re: My Cub Backhoe's PTO shaft

Mon Sep 07, 2009 6:12 am

Well now,,,,,,,,,,,, that's different! :D I would think you should be able to find a splined hub to fit the standard cub pto. Or go ahead and use the shaft you have. I think TSC has the weldable sprockets so replacing your worn ones should be a fairly easy task.

Re: My Cub Backhoe's PTO shaft

Mon Sep 07, 2009 9:47 am

BIgDog:

I am going to use the existing PTO shaft, as it is easier to get a sprocket to fit the 1" keyed shaft, than to find one, or adapt one, to a stock PTO shaft.

I am finding that the 2-ro chain is more difficult to make a sprocket for-at least Tractor Supply, and Surplus Center don;t really have anything that will work, either premade, or weld-on. The weld on hubs don;t accommodate more than 1 sprocket, and sonce my lathe is out of commission right now, it won;t be easy yo make that work.

I ended up buying a stock 1" keyed bore #50 sprocket, with the sprocket at one end of the 1: thick hub, and another #5-0 sprocket witha plain 1" bore, and teh sprocket centered on teh 1" thich hub. I will attache these together with the sprocket teeth lined up, and cut the keyway in teh plain bore sprocket to match the pother one. Then I'll install them on the shaft with teh proper spacers to get te right distance for teh 2-row chain.

This is what the old sprocket looked like:
Image

Re: My Cub Backhoe's PTO shaft

Thu Sep 17, 2009 10:22 pm

I fabbed the new dual-row sprocket yesterday evening, and installed it on the PTO shaft. I also replaced teh PTO bearing, along with installing the missing grease retainer and clip.

When I pulled the PTO off the tractor, the PTO clutch came off the shaft and fell inside teh differential housing. The oil in there looked pretty good, so I figured rather than drain teh tranny and take the rear cover off completely, i would try to fish the PTO clutch out with a magnet. First try was with an extendible "pickup" tool, with a small super magnet on teh end. No good- the straight shaft would not let me get the magnet near where the clutch(apparently) was. I DID get a whole bunch of bits of steel, along with the remians of teh PTO clutch setscrew, and a large thin washer that MIGHT be what is left of teh original grease retainer.

Next I tried a regular magnet on the end of a flexible wire. Again no good-the magnet was not strong enough, and that particular wire was too flexible.

So i fixed another small super magnet(from a disk drive motor) to the end of a larger, heavier piece of wire. With this, i was able to feel the PTO clutch, and I got it dragged back under the differential, when somehow, my new magnet came off of the wire.

So I drained the tranny, removed teh rear cover, and got teh clutch out. I will let it drain overnight, flush with kerosene, and refill with new gear oil.


A question-what holds the PTO clutch setscrew in place? The manual says to tighten it only enough to stop the clutch from coming off the shaft-would a little Loctite be in order here?

Re: My Cub Backhoe's PTO shaft

Fri Sep 18, 2009 6:24 am

Yes - loctite.

Re: My Cub Backhoe's PTO shaft

Fri Sep 18, 2009 7:45 am

The cub pto shaft with a key way rather than splines, was apparently available aftermarket. When I was needing a new shaft several years ago, my local dealer had one in stock, but could not get originals at the time.

Re: My Cub Backhoe's PTO shaft

Sat Sep 19, 2009 9:04 pm

Thanks, Bigdog. I used Blue loctite.

Thanks John-that is interesting about the shaft-I definitely could see no sign of it being welded up or sleeved, so maybe mine is one of those aftermarket ones. I wonder who made them?

I got the thing back together today-I used triple row #50 chain instead of dual row, as it was less expensive at Surplus Center-. It used to clank as it went arond-now it hums.

I will keep it lubed with chain lube, and hope it lasts a long time.

Here is a shot of the old and new sprockets:
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