Front wheel bearings failed L5740

[MHarryE]

Calculating the bearing life is not so simple as looking at the basic load rating. Part of the life equation (revolutions) is a factor of (dynamic load rating/equivalent load)cubed. If the bearing load is the rated dynamic load, this factor is simple - one. If the bearing load is one half of the rated load the life will be 2 cubed or 8 times longer than if running at rated load. Now drive on a side slope and thrust load is added and these bearings are not designed for high thrust loads. Life calculations get very complicated as an example I had the load histogram taken from field test data for a drive. Bearing life was the critical parameter. I gave the histogram data in percentage time at given loads having broke my data into 30 different load ranges. When looking at the computer generated results, only the 3 highest loads were significant. Combined they represented only 5% of the operating life but that cube factor becomes so significant. Yes I run my tractor hard. Bearing life was a concern do I routinely loosed for leaks. I had hoped for better but I am not extremely disappointed with my bearing failure.

 

[Complete Turf Care]

I spent all day loading big rolls of sod into the planter. I estimate these rolls weigh about 1000-1200 lbs each. Hopefully, I didn't break any more bearings.

I did seem to feel a 'chatter' from time to time. I'm thinking that may be the gears that were chewed up pretty good on the first side that I changed.

Well, more work for the tractor today.....I hope it holds up.

 

[SPYDERLK]

I spent all day loading big rolls of sod into the planter. I estimate these rolls weigh about 1000-1200 lbs each. Hopefully, I didn't break any more bearings.

I did seem to feel a 'chatter' from time to time. I'm thinking that may be the gears that were chewed up pretty good on the first side that I changed.

Well, more work for the tractor today.....I hope it holds up.

View attachment 430516

The gears will be fine. ... Just raise the fronts and feel for play occasionally. You dont want any more bearing parts running around loose in there.

 

[rbargeron]

I'd like to offer the group a different mental image of what's going on in a ball bearing - and how failure starts.

Imagine rolling a bowling ball along on top of a bed. After one run, there isn't much evidence of the ball rolling across it. But after many back and forth trips of the ball, the sheets and other coverings get stretched a bit, the top internal layers of the mattress become frayed.

In a ball bearing the same thing is going on - the bearing surfaces are hardened so the deformation is tiny, but it's real. In the grains a few layers below the surface the shear displacement can be significant. The accumulated damage can get to where the ball or the race develops lateral cracks, and microscopic chunks of material break out. After enough of that goes on the bearing gets rough and noisy and eventually may shatter.

The biggest single factor in a bearing's life is how many internal metallurgical defects it has from new. The mean time to failure at "rated load" may be few million cycles, but the standard deviation is large. Sometimes a visually perfect looking bearing has an internal flaw and fails very soon, even at low load. But the average life of the whole bearing population is very long so it's considered an acceptable situation, given the cost of a major redesign of the manufacturing process or a costly inspection program to examine each one made.

Many machines use tapered roller bearings instead of the ball type. Rollers have line contact instead of point contact so the stress is distributed and lower. Car manufacturers switched to tapered roller wheel bearings 65+ years ago when new cars shipped by rail were arriving at dealers with failed ball bearings (from the constant hammering of rail splices). But tractors haven't followed their lead. Kub uses ball bearings extensively and has apparently never seen fit to change.

All of this said, my bet is that for every tractor with a failed wheel bearing there are many hundreds that are fine, even those lifting big loads.

 

[David Devuono]

From many many years of off-roading where water\mud is what we went looking for, I have had a few bearings go out in my days. They always gave plenty of warning. It might be in a large tractor that you have to use a pry bar and dial indicator to see that wear. I know on my B3200 I surely would never hear nothing till it broke due to the HST wine. If those bearings were wearing out, they would have caused some play and took out the oil seal before a major failure. I am guessing its a stress failure. From what I read, a Sod bale is likely less than 1,000 lbs so should not be a workout for your tractor. Also from off-roading experience, we knew that by going with a wider rim that pushes the tire out, you put more stress on the wheel bearings. If I was paying for the repairs, I would not do this work in the future without a verified 1500 lb counterweight. (I am scared now and going to add concrete to my counter weight)

With respect to the chipped ring gear, it will shed metal bits at an excelerated rate. I would try and get a super magnet or two installed to hold some of that metal. Maybe stick one to the drain plug?

 

[MHarryE]

When you said car manufacturers switched to tapered rollers and tractors never followed their lead I was surprised. The first front wheel drive cars in America switched back to ball bearings. I checked and verified - the most popular car in America today, the Toyota Camry, uses a double row ball bearing for the front wheels.

I won't dispute that in general, tapered rollers have longer life, but they have limitations such as speed. Unlike a true spherical roller, they have slippage and generate heat. High speeds and tapered rollers do not mix. Wheel bearings, however, are not high speed.

So it comes down to packaging. Ball bearings do not require precise clearance or preload (depending on load) like taper rollers. They run cooler so lubrication is not as critical - lubricant deterioration.

So our 60 year old Farmalls have tapered rollers and fail if overloaded or not properly serviced. I assume Kubota had a reason for selecting ball bearings (any bearing supplier or bearing design handbook will guide a person through the selection process). Being Japanese, however, they may not realize how North Americans treat their equipment. My experience in Japan, though limited, found very focused operators. They do not tend to use machines to the limits. Can this result in under-designed designs? One would think with all their North American experience they would have learned by now many North Americans use their machine to 110% of its limit.

 

[rbargeron]

........The first front wheel drive cars in America switched back to ball bearings.......

Always nice to read your informed posts Michael. You may be retired but you're not a "former" engineer, you still have an active practice! As often happens I posted a comment without acknowledgment of contrary facts. Bearings are a big subject - maybe several library shelves (or servers). Mostly I was trying to get people away from thinking the first time they lift something heavy their bearings will fail. Years ago I looked into Hertz contact stresses for crane rails & wheels that see 250,000 psi. Failure starts well below the surface - similar situation with rolling bearings. Take care, Dick B.

 

[Complete Turf Care]

Well, it's been just over 3 years, and it happened again today. Right front wheel fell off. Bearings are gone. I guess I am putting too much weight on the front with the loader.

 

[MHarryE]

Well, it's been just over 3 years, and it happened again today. Right front wheel fell off. Bearings are gone. I guess I am putting too much weight on the front with the loader.

Not too much load, too much load for long bearing life. Reducing the load will increase bearing life, but a person could weigh replacing bearings every 3 years versus carrying half bucket loads. Fortunately the bearing is an easy job for do it yourselfers. My dealer told me he has a customer hauls in the front drive assemblies every 2 years and has them rebuilt. Uses his Grand L in a low clearance building to clean manure and feed large bales.

 

[Complete Turf Care]

Ordered the parts today from Messicks. About $575 for everything. The most expensive part is the bevel gear at about $280 and the 'axle' is about $150. My wife works at a local tractor dealer (not a Kubota dealer) and that's where it is being repaired.

Last time this happened, the opposite side went out a week after the first one. I'm hoping this doesn't happen again.

 

[buckeyefarmer]

That just shouldnt happen....

 

[Oldpath05]

What pictures I was able to find on the L5740, the front end looks heavy duty compared to my L3400 with knuckle spindles. No one works a tractor harder than I do, mine has 1000 hard hr on it and front wheels are still tight but guess that could change quick if I dont keep an eye on it. How many hr now on your tractor since the last time the bearings went? I see the first time was around 500+ and that was way to early IMO......

 

[Complete Turf Care]

How many hr now on your tractor since the last time the bearings went? I see the first time was around 500+ and that was way to early IMO......

It is at about 1350 hours now.

 

[repete]

I spent all day loading big rolls of sod into the planter. I estimate these rolls weigh about 1000-1200 lbs each. Hopefully, I didn't break any more bearings.

I did seem to feel a 'chatter' from time to time. I'm thinking that may be the gears that were chewed up pretty good on the first side that I changed.

Well, more work for the tractor today.....I hope it holds up.

View attachment 430516

I used to go through a lot of bearings then I took a serious look at the bearing loading when my wheels were in the "reverse" position to make them wider. I realized that in the reverse position I had basically moved the forces from bearing on both bearings to be being supported by mainly the outboard bearing and the inner larger bearing was put in more of a position of balancing the load as opposed to bearing the load. I have had no issues after placing the wheels back in the narrow position.

I am no engineer by any means but having a L2550 for over 5000 hours of hard use has taught me a lot of things in an expensive way. I used to keep a stock of both sized bearings and a seal on the shelf for this. Now the bearings just sit and gather dust.

 

[Complete Turf Care]

Well.....it happened again. A few days ago I noticed the seal was leaking on the left side. I went ahead and ordered bearings, seals, and the o-ring for both sides and changed both sides today. The left side outer bearing was bad and probably would have failed catastrophically in a short time. All the other bearings were still in good condition.

I'm just glad I noticed the leaking before the wheel fell off this time.

By the way, I now have 1844 hours on the tractor. So the front bearings have failed at roughly 500 hours, 1350 hours, and at 1844 hours. Maybe I should trade this tractor???

About a year ago, i purchased a skid steer and use it for most of the work I was doing with the front end loader on this tractor. However about a month ago, I did use this loader to load a pretty heavy roller onto my trailer. I assume thats what caused it to fail this time.

 

[amhicks21]

ive had front axle bearings fail on 3 of the 6 kubotas that ive run over the years despite them all getting their proper fluid changes. The 2016 l6060 had the bearings go out under warrantee and was traded in at 2200 hours and the 2020 l6060 that i run now had the front dif blow up suddenly and without warning at 50 hours. aside from that ive had to do bearings on a b2920 with less than 500 hours and an l3540 with around 1200. im convinced that kubota front axles just dont stand up to the kind of use that contractors put them through. For us, I think climbing curbs with a full bucket is a big culprit. fortunately they're pretty easy to fix if caught early.

You may not want to trade it right now unless you know they have a replacement in stock. My boss ordered an lx3310 months ago, and they have the tractor in stock but are saying the loader wont be here before winter and the closest dealership with one that has a loader wants 4500 bucks more.

 

[MHarryE]

Well.....it happened again. A few days ago I noticed the seal was leaking on the left side. I went ahead and ordered bearings, seals, and the o-ring for both sides and changed both sides today. The left side outer bearing was bad and probably would have failed catastrophically in a short time. All the other bearings were still in good condition.

I'm just glad I noticed the leaking before the wheel fell off this time.

By the way, I now have 1844 hours on the tractor. So the front bearings have failed at roughly 500 hours, 1350 hours, and at 1844 hours. Maybe I should trade this tractor???

About a year ago, i purchased a skid steer and use it for most of the work I was doing with the front end loader on this tractor. However about a month ago, I did use this loader to load a pretty heavy roller onto my trailer. I assume thats what caused it to fail this time.

Engineering wise - bearing life calculation has one factor load cubed. That means as you reach the highest loads, bearing life drops like a rock. Improved lube will help during normal operation but in high load apps, bearing life plunges. I consider high load as carrying heavy bucket loads with no or little ballast behind the rear tires. I can’t draw a vector diagram for you, but wheel weight like cast iron or liquid does nothing to reduce front tire load. It only keeps the rear tires down to increase stability. Getting ballast behind the rear tires works as a lever to unload the fronts.

My bearing failures were while snow plowing, but after a summer of lots of load and carry moving dirt 100 yards, many tons.

I can scan vector diagrams from my engineering references, but the bottom line will be the same. Keep replacing bearings unless you rebalance your machine. Don’t widen the front tread. Keep spare bearings. Make a YouTube video of how you do it. Sell your YouTube time to pay for parts.

My dealer confirms to me he has many customers who know about when to expect failure, remove the entire assembly and take it to his shop to repair. Kubota probably has lots of failure data - when does it pay to redesign? If redesigned, will our fabulous turn radius turn to intolerable? My M7 has large planetary front finals. My turn radius has to be 3 times that of my L6060, or maybe even more.

My L6060 solution has been to buy a SVL-75-2. So I haven’t failed bearings on the SCU.

 

[buckeyefarmer]

Thanks for documenting this, just in case I need to do it one day on my L3940.

 

[SPYDERLK]

Well.....it happened again. A few days ago I noticed the seal was leaking on the left side. I went ahead and ordered bearings, seals, and the o-ring for both sides and changed both sides today. The left side outer bearing was bad and probably would have failed catastrophically in a short time. All the other bearings were still in good condition.

I'm just glad I noticed the leaking before the wheel fell off this time.

By the way, I now have 1844 hours on the tractor. So the front bearings have failed at roughly 500 hours, 1350 hours, and at 1844 hours. Maybe I should trade this tractor???

About a year ago, i purchased a skid steer and use it for most of the work I was doing with the front end loader on this tractor. However about a month ago, I did use this loader to load a pretty heavy roller onto my trailer. I assume thats what caused it to fail this time.

Have you researched whether there is a higher load rated low speed bearing in the same size package?

 

[deezler]

Interesting that it keeps happening. I'm doing this repair on one side of my Cub Cadet right now at ~780 hours. I sure hope it doesn't happen every 500 hours, but I probably won't be the owner of it by then anyway.

You should probably jump out of the L5740 before it happens again.... Something dimensionally must be off just enough to cause this, that you aren't going to find or fix.