Front Differntial failure L3940

[GarthH]

Hi all.

I just got bad news from my local dealer. Somehow almost all the gears and bearings on my front differential as destroyed. I don't how or why but suspicious on a 72" front blower and subframe that was sold to me by a dealer. I've had it about 4 years now and every year when I install it I say to myself "boy is that thing heavy for this tractor". Not sure though.

Does anyone have a good source of used parts? I'm looking the entire front differential off the L3940.

Thank you for your assitance.

Garth
306.717.2975

 

[K5lwq]

That is unfortunate and somewhat unusual. I would want to see what everything looks like. If the case is good, one would think you could rebuild that one cheaper and easier than finding a complete unit used. Also, I can’t imagine every gear is damaged beyond use.

 

[GarthH]

I agree. I might need to see it myself. I'm told that almost everything is damaged. On on side I'm told the knuckle, I don't know what connects to it but he tells me that it is unusable. I will ask for pictures.

Of course each front wheel is seen from the cab. I noticed some leaking on the right one during the winter and on the left one just in January. There are no other leaks. When I had the left wheel lockup, I changed the gear lube, I don't know how much came out but maybe 2 qts.

I had a seal leak on the right side back about 5 years ago and had the dealer fix it. He had no negative comments just a seal leaking. Obviously he filled it with fluid at that time.

I didn't check it as there were no leaks prior to last fall and now the winter.

They tell me a gear broke and the pieces were being ground up inside the housing.

Kubota Parts only sell pieces for the diff not the entire thing. Do you know if they might sell the entire diff in "whole good". I have bought tires like that from them, parts price for the tire is quite high but sales can sell the tire and rim together at a much better price.

Good questions

 

[jonsstihl]

Sounds like you are looking for a complete axle assembly. just to get the terminology right. you can search for a tractor scrap yard. my guess is the damage is more isolated to the outer assemblies (bevel gear cases) but hopefully the ground up metal is only in the outer assemblies and didn't get into the center section differential. lots of parts to replace in those outer assemblies and I'm not sure if the castings are still available. the 40 series is starting to get old.

 

[hodge]

I would doubt that it's the weight of the blower. A loader and its uses would put more load on the front axle than a blower, and the majority of owners have/use a loader- without axle damage. I believe that the failure is due to something else.

 

[GarthH]

Some pictures

 

[loggin]

Some pictures

That looks like some pretty sever damage. Wonder if the axle was low on fluid for some time..??

 

[jonsstihl]

that looks bad. Sorry for your loss. I did notice when I changed my front axle oil that the level dropped quite a bit after just running it a little so it is important to check the fluid level fairly often and keep an eye out for leaks. I didn't see any broken housings in the pictures so a good cleaning out and replacing the gears and bearings should get you back up and running but it will be expensive. just compare the cost of fixing to the cost of a new tractor. If the rest of the tractor is in good shape I would fix it. you don't mention how many hours are on the tractor but a 40 series without regen is worth a couple bucks. It may be cheaper to find an axle assembly from a tractor scrap yard.

 

[truckdiagnostics]

https://media.spicerparts.com/cfs/files/media/oQLkxMPRdFt3y2a9W/AXSM-0020.pdf?token=eyJhdXRoVG9rZW4iOiIifQ%3D%3D&store=original

About page 21 starts the failure analysis part. you should be able to look at the failed parts and come up with pretty close to what happens. Fatigue, overloading and low oil all look different when they fail.

 

[masscity]

I have a L3540 with the 6 ft snowblower and subframe. I've had it for 12 winters now and up to 40 hrs of use per winter.

I have the oversized FEL with the 6 ft heavy duty bucket, which puts much more weight on the front axle.

So far no problems, I change the front axle oil with 75w-90 Mobil 1 syn every 400 hrs. My front seals are leaking a little, but I make sure my axle oil level is ok.

I think I have around 850 hrs now and will change the oil again when I take the subframe off.

 

[jonsstihl]

do you road your tractor alot, the gear teeth look worn out. obviously a bearing has failed but the gears seem quite worn as well, perhaps lots of use coupled with a too low oil level. I don't think the front blower caused it specifically but do you run a counterweight while the blower is hooked up? It is a lot of weight up front.

 

[5030]

Kubota front axle assemblies don't contain a lot of fluid to begin with so it's imperative to check and maintain the fluid levels regularly. Looks pretty euchered to me but the housing looks ok. Surprised you didn't feel or hear it actually. Easy to check anyway, the center level plug and a single level plug on each outboard. Takes about 5 minutes total.

 

[jonsstihl]

our L40 series axle only has one level plug, close to the fill plug.

 

[5030]

our L40 series axle only has one level plug, close to the fill plug.

So do both my M9's but... each outboard has it's own fill and level plug as well. That may be different today as mine are pretty old units. In fact, om my M's the outboards are sealed with stationary seals from the axle proper and contain their own fluid

 

[sd455dan]

Some pictures

My 02 cents and I think this common across several brands of CUT's, that is that heavy loading of the front axle in 4x4 is causing stub axle inner or outer ball bearing stamped steel cage to wear / distort just enough to release ball bearing(s) at that point it is just a matter of time till the hard, high carbon chromium steel ball bearings find their way between gear teeth.

Then it gets ugly because the ball bearing is so much tougher than the average cast iron gear teeth, something has to give, so the real carnage begins.

In one of the pics a loose ball bearing is visible. If they look through the destroyed parts I would wager at least one mangled bearing cage will be found.
It sure seems like there should be ball bearings made with stronger tougher cages / larger shafts / larger bearings in general or the manufacturers should/could possibly be using roller bearings.
Not much a guy can do beyond checking/changing the oil often. I like to lift the front tires of the ground occasionally and check each side for any "New" play.

Op, I hope you are able to find a complete front axle at a reasonable price and for no further front axle problems in the future.

One thing is for sure you are not alone on this, it has happened to quite a few CUT owners of several different makes over the years.

 

[mikester]

My 02 cents and I think this common across several brands of CUT's, that is that heavy loading of the front axle in 4x4 is causing stub axle inner or outer ball bearing stamped steel cage to wear / distort just enough to release ball bearing(s) at that point it is just a matter of time till the hard, high carbon chromium steel ball bearings find their way between gear teeth.

4WD engaged, heavy front end loads, and sharp turns is all it takes to break a ring and pinion gear

I learned this expensive lesson on my old CUT. Ag equipment ISN'T construction equipment due to the lighter and less robust design

 

[sd455dan]

4WD engaged, heavy front end loads, and sharp turns is all it takes to break a ring and pinion gear

I learned this expensive lesson on my old CUT. Ag equipment ISN'T construction equipment due to the lighter and less robust design

That is another CUT design difference Very small diameter front 3rd member ring and pinion dimensions.
Some housings aren't even any larger in the center section than the outer axle tubes to house the center differential ring and pinion and spider gear. 50 HP running through very much miniaturized gear sets.
As you said, in 4x4, heavy FEL load, and a turn puts a lot of stress into the front drive and tractors do not have a transfer case (with differential action) in between the front and rear axle, so at least one front tire has to slip during a turn.

 

[5030]

One thing I don't care for as far as Kubota is concerned is they use ball bearings in the outboards. Large ag tractors use tapered roller bearings instead and I always worry about my M9's eating the outboard ball bearings and I keep an eye on the freeplay quite a bit. If the outboard bearings fail (cage or bearings), lifting the front axle and rocking the wheel assembly will tell you immediately if they have failed. Any rocking motion vertically or horizontally will immediately tell you if any internal failure has occured and not only the bearings but the though pin bushings as well. Usually when the pin bushings wear out (they are replaceable sintered sleeves, the outboards will start leaking as the lip seals aren't capable of retaining the gear oil.

I've replaced a few previously. You can do that yourself though it does take removing of the outboards completely but all it takes is a proper sized driver and new sleeves. Same applies to the front drive shaft coupler. I replace them as well. They are secured with a roll pin and are a designed wear point. The output shaft as well as the input pinion shaft is hardened and tempered and the coupler is soft. Using discretion for engaging 4wd and maintaining fluid levels and using gear oil instead of UDT or SUDT in the front axle is the way to go in my opinion.

My 2 cents for what it's worth.

 

[truckdiagnostics]

Using discretion for engaging 4wd and maintaining fluid levels and using gear oil instead of UDT or SUDT in the front axle is the way to go in my opinion.

Could you elaborate on the gear oil instead of the sudt. The stuff is stupid expensive. And from what i am hearing they are pretty straight forward to fix. And if they are failing for shock load issues, don't see where the expensive fluid is getting me anywhere. Chances are I am going to break something long before using sudt makes any sense.

 

[big bubba]

truckdiagonistics: you might consider using 75/90 full synthetic (GL5 as 5030 notes) esp given you're in a colder climate as well. valvoline is at the top of my list, what is your ft axle capacity? btw: if valvoline syn is to costly for you, they also make a conventional 75/90 as well that i use in my older truck... regards