MX 7 Clutch rebuild or replace whole thing?

[bswiv]

Clutch for JD MX 7.........

After twisting off the shaft a couple of weeks ago the cause of that was discovered in the slip clutch, which was rusted and seized up. It being a Friday evening, and there being mowing to be done on Saturday it was decided to tear the clutch down and see if it would be usable.

About 3 hours of work rendered a clutch that was for sure only good for a short while. All the parts were rusted and pitted and a the clutch disks themselves ( 4 ) were not good, a couple being cracked.

Cleaned the heck out of it, filing and sanding down the metal bearing surfaces and then cleaning up the disks as best as possible.

So today while mowing a fire break ( we are forestry ) it failed catastrophically, simply ate up all the disks.

Took it apart this afternoon.

Disks are about $20-25 each.......and it takes 4.

So my question is......how smooth do the metal bearing surfaces for the disks have to be?

Buying the whole thing is EXPENSIVE.......but then if I get the disks and they get ate up in no time, that's not a win either.

Suggestions?

 

[pmsmechanic]

This is a text book case for why I like sheer bolts instead of a slip clutch. A lot of people won't agree with me and that's fine.

You need to decide why the discs disintegrated. Is it because of the rough surfaces or is it because of poor discs. Also did you maybe over compensate and run your clutch springs too loose? The clutch should only slip when you hit a rock or some other immovable object. If it was slipping the whole time you were using it then a whole new clutch isn't going to solve the problem.

 

[bswiv]

This is a text book case for why I like sheer bolts instead of a slip clutch. A lot of people won't agree with me and that's fine.

You need to decide why the discs disintegrated. Is it because of the rough surfaces or is it because of poor discs. Also did you maybe over compensate and run your clutch springs too loose? The clutch should only slip when you hit a rock or some other immovable object. If it was slipping the whole time you were using it then a whole new clutch isn't going to solve the problem.

Surfaces are somewhat rough.

It was probably slipping a lot more than it should have been as when I put it back together after cleaning it up I may have overcompensated for the fact of it having been seized up before.

Bellvile spring ( spring washer ) is what it has, just the one.

Mowing fire breaks in woods so hitting things.......with the occasional fatwood stump, which might as well be a rock. It was a fatwood stump that I originally sheered the shaft off on a couple of weeks ago.

So how smooth do the surfaces have to be? Like glass? They are pitted from where it rusted up previously......though I filled and sanded them down such that they were slipping.

 

[pmsmechanic]

I think as long as the surfaces don't have anything sticking out of them that can tear up the disc then it would be ok to use them.

The owners manual should have a section on how to set up and maintain a slip clutch. If you don't have one then John Deere has their owners manuals on line as a free download.

 

[JRobyn]

I just rebuilt the Bondioli&Pavesi (sp?) slip clutch on my bushhog. I replaced the one rear metal disk/friction surface that was horribly rusted ($52); the front (drive) disk surface was slightly rust-pitted, but no worse than an old brake disk. The steel center "hub" front surface was about like the drive disk, the rear face was BADLY rust pitted. A replacement was about $218). I had a machine shop take 0.020" off the back and it still looked pretty horrible, so another 0.020" came off. This left just a few of the major pits. It's all back together now and working great, but no telling how it will hold up over time. Since it really shouldn't slip very much, I'm guessing it will do fine. It's not like an automotive disk brake, although it functions similarly.

From the as-found condition, what really ate mine up was that the rear friction disk wore completely out (was GONE) so the steel surfaces had nothing between them but water and rust. I believe that one spell of running it with the springs too loose is what ate the rear friction disk.

If many of your parts can't be rescued by machining, I agree that replacement parts are horribly expensive, and a complete replacement would make more sense. I assume JD is even worse than B&P. Did Deere actually make your clutch? I did see some aftermarket complete clutches in the $125-$200 range.

 

[pmsmechanic]

I'll go along with JRobyn. When I replaced the slip clutch on my 660 rototiller the John Deere parts were quite a bit more expensive than parts from Walterscheidt. I didn't get exactly the same clutch but the function was the same. The Walterscheidt clutch tightened onto the gearbox shaft with bolts and the original John Deere clutch slipped on like a pto shaft. Other than that everything else was the same

 

[bswiv]

Thank you for the input. Does seem that one or two parts are worse than the others so I'll see if I can get just those......and new disk plates obviously.


This is a sticking point though...........I am having a hard time finding the JD Part Numbers.......it's like with Caterpillar......almost as if they hide them so it's hard to get replacements from other places!!!......any suggestions on how to find for this unit?

 

[bswiv]

Okay.......ignore the part about not finding part numbers......just found it.......and I owe JD a apology as it was on their site!!

 

[Kyle_in_Tex]

I wouldn't worry so much if the parts are lightly rusted, as any slippage will clean them off. But the fact that they were rusted and locked up is why you have to sometimes back them off and loosen the disks if they have been sitting a long period. If they are warped, and there is enough material to machine them down, go for it.

 

[JRobyn]

One tip I found - when I went to get my "center hub" turned down, I figured it was an easy job for any competent auto machine shop. Evidently not. The best shop in town took one look at it and said "we can't do that - take it down the road to the transmission shop with a brake lathe" (it looks similar to a front disk brake hub/disk). The trans shop took one look and said "we can't do that - it's too small to fit on our lathe". Wound up at the very fine local metal fab shop who easily chucked it in what appeared to be a regular lathe and cut it down. It did cost me $65 in shop time, so maybe they had to fiddle a little to get it chucked in good.