Third B7100 clutch in 4 years!?!?

[torch]

January 25, 2019. My clutch friction plate self-imolated. Tractor suddenly started making a horible metallic rattle, like the fan was hitting something, then shortly thereafter siezed. A spring broke and jammed the clutch against the housing. I replaced the friction plate, pressure plate assembly, throwout bearing, dust seal and pilot bushing with all OEM Kubota parts. The flywheel was fine when checked on a surface plate.

December 29, 2020. It happened again. As soon as I heard the noise, I recognized it, parked the tractor and split it, finding the friction plate spring assembly had fractured in a similar manner. Replaced it with another OEM friction plate. Also replaced the gasket with OEM. Everything else was fine. Clutch worked great.

Until yesterday, Dec. 25, 2022. I fired up the tractor, let it warm up for a few minutes, unplugged the block heater, reduced engine speed to idle, depressed the clutch and engaged the PTO. As I released the clutch I instantly recognized the same old sound. I quickly depressed the clutch and disengaged the PTO and the tractor seized.

I had spent about 6 hours the day before clearing the deep (2-3') but light snow left by the blizzard. There were no signs of problems. The tractor was under load to be sure, but I kept the travel speed down no shock loads - I didn't break any shear bolts on the blower anyway.

The only thing I never replaced in there the first time was the flywheel. But it checks out fine and it's no longer available from Kubota anyway. The transmission input shaft had no sign of play last time, so I doubt that's the issue. The tractor is an HST model, so the clutch gets used rarely -- starting, changing range and engaging or disengaging the PTO.

Of course, the Kubota dealers are both closed for the holidays, so I can't order parts today anyway, but I'm starting to wonder if I'm wasting my money on OEM. There are aftermarket friction plates available and usually I shy away from that sort of thing but I'm beginning to wonder if they are really any worse? Is there a heavier-duty option out there?

 

[DustyRusty]

Is the clutch plate marked in the direction that it should be installed? There has to be something that is causing the spring or springs to fail, and my first thought would be that the clutch plate is improperly installed. Usually, when this happens, the clutch won't work, but not being familiar with your application, is just a guess. Do you still have the previous clutch disks that you can compare with each other to see if the failures are both identical? The Kubota dealership mechanic might be of more help in this matter than the fellows behind the parts counter. They might have encountered this issue before.

 

[Vigo]

So as an auto tech ive replaced a lot of clutches and other than wearing out the lining (best case scenario) the 2nd leading cause of clutch replacement ive seen is damper spring failure. So im here to tell you, they’re probably going to break regardless of how you treat it.

On cars you can be a bit picky because there is usually a variety of versions of the same part available, and the design of the clutch hub varies as far as how well ‘retained’ the damper springs are. Most are only ‘cupped’ at each end and if the spring breaks it is free to fall out. Others are ‘fully caged’ where the spring is only visible through a hole in the side of a cylinder of metal covering it. In those designs if the spring breaks it does not fly out. I would guess almost noone knows to look for this other than people who have personally replaced a lot of clutches. Now whether there exists enough variety of Kubota clutch disc designs, that one such is available for a b7100, is the real question. Lots of times parts listings dont show a picture of THE actual specific part in question, so it can be hard to know. On cars it is easy because Rockauto.com exists and they have the best parts website known to man!

There also exists such thing as an ‘unsprung hub’ with no damper springs in the clutch plate, but usually a vehicle is only converted from a sprung hub to unsprung hub for racing/competition purposes, because it does make the vehicle a little less pleasant to operate. But it massivey increases the reliability of the clutch hub! Some cars have unsprung clutch hubs from factory, but it generally only because the damping function has been moved to the flywheel in the form of a ‘dual mass’ flywheel, which is an even more expensive part to replace when its damping function fails.. which it does!! I have a Mazdaspeed6 i bought with 23,000miles which already had a failing dual mass flywheel, and still does at 31k.


The purpose of the damping springs is related to the separation of power pulses in an engine. In general, the less cylinders an engine has, the ‘further apart’ its power pulses are, so its conceivable a 3 cyl operating at low rpms ‘cycles’ its damper springs hard because they might have time to fully relax before being pounded again, whearas if the pulses come quick enough the spring might spend more time cycling ‘shallowly’ over only part of its travel because it wouldnt have time to fully extend again. That’s just a weak theory.

As for what you can do.. to stop them breaking? I dont know, nothing. I do know rust forms stress risers on springs which lead to cracking so refuse delivery of any part with rust visible on the springs. What i would do if i couldnt find a better built clutch disc is just modify it to encapsulate the springs better so when they break it’s somewhere from unnoticeable to annoying rather than rendering the tractor inoperable and risking further damage/FOD. Should be able to weld small covers to the disk easily enough. I wouldnt personally worry about balance but you could have it checked. My .02.

 

[torch]

For reference, here is the first failed friction plate:

And here is the second one:

 

[#40Fan]

How high of an engine speed are you engaging the clutch PTO?

 

[torch]

Idle. Always.

 

[Dave_eng]

January 25, 2019. My clutch friction plate self-imolated. Tractor suddenly started making a horible metallic rattle, like the fan was hitting something, then shortly thereafter siezed. A spring broke and jammed the clutch against the housing. I replaced the friction plate, pressure plate assembly, throwout bearing, dust seal and pilot bushing with all OEM Kubota parts. The flywheel was fine when checked on a surface plate.

December 29, 2020. It happened again. As soon as I heard the noise, I recognized it, parked the tractor and split it, finding the friction plate spring assembly had fractured in a similar manner. Replaced it with another OEM friction plate. Also replaced the gasket with OEM. Everything else was fine. Clutch worked great.

Until yesterday, Dec. 25, 2022. I fired up the tractor, let it warm up for a few minutes, unplugged the block heater, reduced engine speed to idle, depressed the clutch and engaged the PTO. As I released the clutch I instantly recognized the same old sound. I quickly depressed the clutch and disengaged the PTO and the tractor seized.

I had spent about 6 hours the day before clearing the deep (2-3') but light snow left by the blizzard. There were no signs of problems. The tractor was under load to be sure, but I kept the travel speed down no shock loads - I didn't break any shear bolts on the blower anyway.

The only thing I never replaced in there the first time was the flywheel. But it checks out fine and it's no longer available from Kubota anyway. The transmission input shaft had no sign of play last time, so I doubt that's the issue. The tractor is an HST model, so the clutch gets used rarely -- starting, changing range and engaging or disengaging the PTO.

Of course, the Kubota dealers are both closed for the holidays, so I can't order parts today anyway, but I'm starting to wonder if I'm wasting my money on OEM. There are aftermarket friction plates available and usually I shy away from that sort of thing but I'm beginning to wonder if they are really any worse? Is there a heavier-duty option out there?

Torch
You have made a loader for your B7100 from memory.
Something serious must be wrong with alignment because you are not a novice who does not know how to use a clutch. The clutch disk failures look like something is bent or bending under load and the clutch disk is trying to deal with mating to the flywheel at an angle.

I am suggesting you start checking the bell housing for cracks.
The forum has a historic case where a bell housing was cracked from stresses from a loader

Do you have a backhoe on the B7100?

Dave

 

[fried1765]

January 25, 2019. My clutch friction plate self-imolated. Tractor suddenly started making a horible metallic rattle, like the fan was hitting something, then shortly thereafter siezed. A spring broke and jammed the clutch against the housing. I replaced the friction plate, pressure plate assembly, throwout bearing, dust seal and pilot bushing with all OEM Kubota parts. The flywheel was fine when checked on a surface plate.

December 29, 2020. It happened again. As soon as I heard the noise, I recognized it, parked the tractor and split it, finding the friction plate spring assembly had fractured in a similar manner. Replaced it with another OEM friction plate. Also replaced the gasket with OEM. Everything else was fine. Clutch worked great.

Until yesterday, Dec. 25, 2022. I fired up the tractor, let it warm up for a few minutes, unplugged the block heater, reduced engine speed to idle, depressed the clutch and engaged the PTO. As I released the clutch I instantly recognized the same old sound. I quickly depressed the clutch and disengaged the PTO and the tractor seized.

I had spent about 6 hours the day before clearing the deep (2-3') but light snow left by the blizzard. There were no signs of problems. The tractor was under load to be sure, but I kept the travel speed down no shock loads - I didn't break any shear bolts on the blower anyway.

The only thing I never replaced in there the first time was the flywheel. But it checks out fine and it's no longer available from Kubota anyway. The transmission input shaft had no sign of play last time, so I doubt that's the issue. The tractor is an HST model, so the clutch gets used rarely -- starting, changing range and engaging or disengaging the PTO.

Of course, the Kubota dealers are both closed for the holidays, so I can't order parts today anyway, but I'm starting to wonder if I'm wasting my money on OEM. There are aftermarket friction plates available and usually I shy away from that sort of thing but I'm beginning to wonder if they are really any worse? Is there a heavier-duty option out there?

Just to add some confusion.:

I bought an aftermarket clutch assembly for my Ford 1920.
Clutch was not troublesome, but thought I would replace it while I had most of the tractor apart.
Aftermarket clutch lasted 2-1/2 hours (broken spring)..
Replaced with another, from different aftermarket source
All is good to date.

 

[torch]

Torch
You have made a loader for your B7100 from memory.

Yes. And yes, I have a backhoe, although that was added to the collection after the second clutch failure.

Something serious must be wrong with alignment because you are not a novice who does not know how to use a clutch. The clutch disk failures look like something is bent or bending under load and the clutch disk is trying to deal with mating to the flywheel at an angle.

I am suggesting you start checking the bell housing for cracks.
The forum has a historic case where a bell housing was cracked from stresses from a loader

I will have another look, but there was no sign of such the last time. I take your point though, It does kind of look like metal fatigue from bending back and forth.

I'm not sure how much angular stress could be transmitted to the friction disk if the bearings on either end of the shaft (ie: pilot bearing and input shaft bearing) are in good shape. The shaft should keep the clutch aligned with the crankshaft.

I wonder if the flywheel is running true with the crankshaft...

 

[woodman55]

Do you remember how hard/easy it was to slide the tractor back together. If it was hard to line things up, it might be a indication of misalignment.

 

[North Idaho Wolfman]

I've had excellent luck on both my B's and L's with aftermarket clutch assemblies, and if I remember right they both looked heavier than stock.
This is who I've always gotten them from:

FITS KUBOTA B6000 B4200 B5100 B6100 B7100 TRACTOR CLUTCH kit No pilot | eBay

Find many great new & used options and get the best deals for FITS KUBOTA B6000 B4200 B5100 B6100 B7100 TRACTOR CLUTCH kit No pilot at the best online prices at eBay! Free shipping for many products!

www.ebay.com

I'll look in my parts stash and see if I have a spare flywheel hanging around.

 

[torch]

Do you remember how hard/easy it was to slide the tractor back together. If it was hard to line things up, it might be a indication of misalignment.

It wasn't too difficult, but there is a trick to it -- the front driveshaft is not level, it comes in on an angle. So it's a matter of lining that up at the same time as lining up the shaft into the clutch. Once the angles are right, it just slides right in.

 

[torch]

I've had excellent luck on both my B's and L's with aftermarket clutch assemblies, and if I remember right they both looked heavier than stock.
This is who I've always gotten them from:

FITS KUBOTA B6000 B4200 B5100 B6100 B7100 TRACTOR CLUTCH kit No pilot | eBay

Find many great new & used options and get the best deals for FITS KUBOTA B6000 B4200 B5100 B6100 B7100 TRACTOR CLUTCH kit No pilot at the best online prices at eBay! Free shipping for many products!

www.ebay.com

Interesting. Even with $120 shipping to Canada, that's still far less expensive than the one from Kubota.

 

[North Idaho Wolfman]

Interesting. Even with $120 shipping to Canada, that's still far less expensive than the one from Kubota.

I have 3 L's and 4 B's that have been running setup's from him ( Jeff Cube ) and no failures.

 

[torch]

I pulled the trigger and ordered one from Jeff Cube. Won't be here until mid-January though. I'll order another from the Kubota dealer if they have them in stock -- if so, it's usually only 2 days although hard to say with New Years coming up. I'll install whichever arrives first and the other will be a spare.

I'll take measurements of each and compare to see if there is any discernible difference in material thicknesses. That's not the only metric of build quality of course, but I'm limited in what I can do in terms of further testing. Other than the one destructive ultimate test I keep repeating, of course.

 

[woodman55]

Any chance you could mount a dial indicator, and check the flywheel in a few places for runout/warpage ?

 

[Vigo]

Those pics are instantly familiar.. design looks like 95% of every car/truck clutch disc ive ever replaced in the last 20 years. Same design, same problems, same old story. At least you haven’t beaten Fried1765’s “record” of a 2.5 hr service life!

I wouldn’t worry too much about alignment, bending, fatigue etc. The entire clutch disc assembly is quite floppy by nature and even just the runout allowed by the clearance between the hub splines and input shaft splines would be alarming if you didn’t ‘know better’. Alas, it’s normal and it all works. Pressure plates usually have their friction surface suspended by ‘straps’ too, which is vaguely alarming the more you let yourself think about it. Y’all know about the Marcel spring? There’s a ton of flex built into the clutch assembly to make it engage smoothly without chattering. Ive actually replaced a a normal ‘sprung hub full face organic clutch disc’ like that with an unsprung hub ceramic puck clutch with no flex at all, so ive been on both sides of what those parts do. Ive got a buddy who has had pressure plates modified with extra straps after bending them with a high rpm misshift while drag racing. I have a 1990 Plymouth Voyager minivan with a manual transmission (and a turbo..) that has a ‘dual diaphragm’ pressure plate which means the pressure plate was modified to include a 2nd diaphragm spring and the friction plate surfaced accordingly to regain the clearance eaten by the additional spring. It is essentially ‘twice as stiff’ as stock and clamps the clutch disc twice as hard, while also giving my leg twice the workout.

Anyway, ive gone down the clutch rabbithole plenty. I wish you luck with the next one!

 

[fried1765]

I pulled the trigger and ordered one from Jeff Cube. Won't be here until mid-January though. I'll order another from the Kubota dealer if they have them in stock -- if so, it's usually only 2 days although hard to say with New Years coming up. I'll install whichever arrives first and the other will be a spare.

I'll take measurements of each and compare to see if there is any discernible difference in material thicknesses. That's not the only metric of build quality of course, but I'm limited in what I can do in terms of further testing. Other than the one destructive ultimate test I keep repeating, of course.

Installing a new clutch, and then also buying another for a "spare".
Clutch paranoia ?

 

[torch]

Any chance you could mount a dial indicator, and check the flywheel in a few places for runout/warpage ?

Oh absolutely!

 

[torch]

Installing a new clutch, and then also buying another for a "spare".
Clutch paranoia ?

Given the rate I'm going through them, can you blame me? <lol>