M9540/9960 PTO Brake Problems

[SDT]

I own a 2015 M9960.

Today, I was at my local Kubota dealer investigating bat wing mower options.

While there, I noticed a split M9540 in the shop. As it turns out, the 9540 had been split to repair/replace the PTO brake. I inspected the damaged parts and learned that the failure was catastrophic.

After speaking with the service manager, I learned that there is a known problem with the PTO brake in 9540 and 9960 tractors with serial numbers prior to (at least) 62438. Of course, my 2015 9960 with about 46 hours but out of warranty on elapsed time, is prior to the SN break.

Apparently the PTO brake design is not robust enough to withstand PTO disengagement with a substantial inertial load connected (bat wing mower, etc.). After inspecting the damaged parts in my dealers shop, I agree. FWIW: I was a design engineer for GM for many years and a failure analysis engineer for the last couple of years before retirement.

Kubota has made changes to the PTO clutch/brake assembly subsequently to SN 62438 (edit: typo). Apparently, this is a known issue. Repair parts for tractors prior to the SN break result in an order of a "service pack" PTO clutch assembly, without detail of changes made therein.

Relatedly, I was informed by my dealer's service manager that Kubota does not recommend operation of bat wing mowers with 9540/9960 and related tractors due to this design defect.

WHAT? There is no such notification of bat wing mower prohibition in any of the related Kubota marketing literature. Indeed, there are multiple photos of similar tractors pulling bat wing mowers.

FWIW: I am currently in the market for a 12' or 15' bat wing mower for use with my M9960.

Of course, I have the common sense to return engine/PTO RPM to idle before disengaging the PTO, but, unfortunately, the electric over hydraulic PTO control switch is situated close to the operator's right elbow. Consequently, inadvertent full power PTO disengagement is unavoidable due to inadvertent bumps of the PTO switch by the operator.

Again, this appears to be a well known issue. Apparently, Kubota has decided to address this issue on a case-by-case basis rather than recalling all tractors with the well known design defect to update such machines to subsequent design standards.

My M9960 with less than 50 hours is out of warranty due to elapsed time.

Currently, I am shopping for a bat wing mower to replace the Woods BB740X 7' mower currently used with my M9960.

This presents a dilemma.

Anyone know if Kubota is or might be planning to recall affected tractors to address this issue?

Thanks in advance.

SDT

 

[SDT]

The parts to repair the failed PTO brake on the M9540 at my dealer arrived late yesterday. This morning I visited to view the design changes before they installed the assembly.

The repair involves replacing the entire PTO clutch assembly with the upgraded design used on late model M9960 and later tractors. The brake disc is thicker and probably made of better steel, though it is not possible to determine that visually. The tab stop that prevents the PTO clutch disc from rotating, once part of a casting that supports the clutch assembly and includes the PTO clutch relief valve, has been replaced with a hardened steel dowel pin and the design of the relief valve has been changed. A new steel shield covers the brake assembly for whatever reason. The upgrade kit costs around $1,000.

Tractors are being serviced on an as failed basis. There is no recall. The 2014 tractor at my dealer is within warranty on hours but well out of warranty on elapsed time. Kubota is covering none of the repair/upgrade costs. I was told that the repair bill for this tractor, a 2 WD cab model, will probably be $3,000+.

I'm considering installing a HD PTO over running clutch on my M9960 when I buy my bat wing mower. Hub City makes a HD one rated for 150 HP but it retails for over $400.

SDT

 

[jdjdjd]

I have a M9540 Cab and a Rhino 15' Batwing mower that I bought new in 2006. I also have a Hay Baler and Cutter but they both have an overrun built into the shaft. Never thought about the Shredder but it makes sense, even at low speeds it has a lot of inertia. An overrun coupler sounds like a good idea. My manual for the batwing mower shows a very specific measurement of 14" from the end of the PTO shaft to the drawbar mounting hole for the proper operation of the CV Joint. If you add the overrun coupler you may have to add a longer drawbar.
For info I have about 1800 hours on my tractor, about half that is running the 15' shredder.
I am curious to hear from others about this issue.

 

[Poopdeck Pappy]

I'm bumping this old thread back to life. Has anyone heard any more about this issue? Has anyone on here actually experienced this problem with their 9540 or 9960?

 

[SDT]

I'm bumping this old thread back to life. Has anyone heard any more about this issue? Has anyone on here actually experienced this problem with their 9540 or 9960?

I've had no issues with my 9960 but it has only about 50 hours on it and I'm very carefully how I turn it off.

I did meet the Kubota regional technical representative in June or July and spoke to him at length about it. He was very careful about what he said and how he said it but it was obvious that Kubota is well aware of the issue, and, indeed, has redesigned the PTO clutch/brake.

There will be no recall.

SDT

 

[diesel85]

This is interesting. My flail mower has a built in over running clutch inside the gearbox -- no adapters necessary. I wonder why an expensive batwing mower wouldn't have this standard?

 

[Poopdeck Pappy]

SDT, do you know if this affects the 8540 also?

 

[SDT]

This is interesting. My flail mower has a built in over running clutch inside the gearbox -- no adapters necessary. I wonder why an expensive batwing mower wouldn't have this standard?

I've never seen one that did.

SDT

 

[SDT]

SDT, do you know if this affects the 8540 also?

I do not but would certainly expect so.

SDT

 

[big bubba]

have an 8540 w/serial 5xxxx so mine probably has the same design fault. would be interesting to hear from those M series owners in the 85-9540 series if this problem has occurred w/rotary cutters/ balers, etc other than bat wing models. no doubt it has to do w/the inertia.

i'm always careful on my twin spindle 8' hog to let the pto rpm settle to near idle speed before disengaging pto. same w/engaging. know most operators already practice this, but just to say. sorry to hear of the repair cost