B7800 - Busted Axle at 441 hours

[riptides]

If it broke like the one in the first post its not that big of a deal to fix(not that it makes it okay). I'm not sure why these failures have been happening, but I tend to think it is more of a defect than operator error.

All the parts needed cost less than $200 (stub shaft, 2 bearings, seal, etc), and if you are mechanically inclined it should only take a couple hours to fix. Just make sure you set the shims right for the case gear (the WSM tells how to do all this). I can't believe the prices some people pay for parts/labor for relativly minor things. To the average person it seems like a catastrophic failure which is why the dealers take advantage of people and charge them big $$$ to fix things like this.

...

Appreciate the insight, will have to do labor myself if the dealer cannnot help me out.

Was moving on level ground, taking a slow turn. Next thing I know, I hear a pop and ate dirt.

 

[irwin]

Appreciate the insight, will have to do labor myself if the dealer cannnot help me out.

Was moving on level ground, taking a slow turn. Next thing I know, I hear a pop and ate dirt.

riptides...Not that it should matter too much, but were you in 4wd when it broke? and to the other guys with similar failures do you leave it in 4wd regularly? Was it in 4wd when it broke?

I'm really interested if there's a connection in these breakages. No' I don't think using 4wd on dirt or a lawn should lead to front axle failure, just interested if it was a factor... Repetitive stress on a minor defect in a part.. I say minor defect because it took 400 hours before the failure occured.. Huhh?

 

[riptides]

irwin To answer your questions, yes, I was in four wheel drive. I was making a slow turn to the left, when it snapped. Ground conditons were very dry on that spot.
I was in four wheel drive because in that area I have to cross a creek bed, with a slight incline going up hill.

It was the outer wheel that snapped clean off, as I was making the turn to the left.

I called the dealer and, well, not covered, and they have seen this failure before. Same circumstances, 4wd, outer wheel axle snap on turn.

I will be working with them, I will get the hub/axle off and take it to them for repair. Sort of a half and half proposition to keep the costs down.

I have never really stressed this machine, but the area that I mow is unique, lots of kidney stone remover bumps, standing pools of water, mud and extreme dry conditions.
I mow slow, but it is bumpy. I might have to rethink tractor use in this area. I do have some other tractors that are bigger, so they may have to come into play.

Disappointed, I just don't feel the break is "justified" for what I have done and what I was doing with this machine.

 

[rScotty]

irwin To answer your questions, yes, I was in four wheel drive. I was making a slow turn to the left, when it snapped. Ground conditons were very dry on that spot.

Disappointed, I just don't feel the break is "justified" for what I have done and what I was doing with this machine.

From your description of the use, I also agree that it shouldn't have failed. But it did...and now the problem is how to keep the next one from doing the same. Your usage sounds normal enough....and besides, you need to use the machine that way.

It might have been a defective part that started the initial high stress point. Fractures always start somewhere and that is easy to identify. To my mind anything that lasts 400 tractor hours fails because of repeated stress - the typical "fatigue failure". If so, that is pretty easy for a metallurgy lab or any experienced older engineer to spot. Often adding a simple radius or doing some polishing can significantly improve the life of the part. John Deere publishes a booklet in their Fundamentals of Service (FOS) series on how to examine broken parts to determine the cause of failure. JD is very proactive on thoroughly training their mechanics. The particular book I'm thinking of is a soft cover with many good pictures and JD's typical complete discussion. Worth buying. I'd hope that all the serious tractor brands have similar programs.

If it were mine, I'd be sure to check the outer and inner axle bearings that mount that broken stub axle. And also check the differential planetary gears in the front axle to make sure they rotate very smoothly. High friction in any of the gears or bearing surfaces I've just mentioned will cause the axle torque to "lag" or drag relative to the tire on the ground. If the axle is lagging due to internal friction of some kind, then the normal rotation of the tire against the ground will put a lot of extra twist onto that axle.

You might not be able to tell why it failed, but it's worth a look. Most mechanics I know got into their trade by being curious about why things work.....though sometimes it's easier to figure out why than to do anything about it.
rScotty

 

[Verticaltrx]

irwin To answer your questions, yes, I was in four wheel drive. I was making a slow turn to the left, when it snapped. Ground conditons were very dry on that spot.
I was in four wheel drive because in that area I have to cross a creek bed, with a slight incline going up hill.

It was the outer wheel that snapped clean off, as I was making the turn to the left.

I called the dealer and, well, not covered, and they have seen this failure before. Same circumstances, 4wd, outer wheel axle snap on turn.

I will be working with them, I will get the hub/axle off and take it to them for repair. Sort of a half and half proposition to keep the costs down.

I have never really stressed this machine, but the area that I mow is unique, lots of kidney stone remover bumps, standing pools of water, mud and extreme dry conditions.
I mow slow, but it is bumpy. I might have to rethink tractor use in this area. I do have some other tractors that are bigger, so they may have to come into play.

Disappointed, I just don't feel the break is "justified" for what I have done and what I was doing with this machine.

What year is your tractor? I went back and looked at my parts books and it looks like the earlier B7800s did use a different stub shaft that is now obsolete (66591-5656) May have been a weaker part so they upgraded. I know the B3200, B3030, and the B26 all use this newer stub shaft and I have yet to hear about a failure on one of them. Also, there's no point in taking the hub/axle off and taking it to them, once it's apart your almost done with the job.

Don't worry about how you were/are using the tractor, remember it is a tractor and is meant to be used like this. When things break fix them and move on. I bet you won't have any trouble with the new stub shaft...

 

[riptides]

rscotty Thanks for the information.

Verticaltrx It is the first year model, 2003. Since I was talking to the dealer over the phone, the bring the parts into the dealership was curious to me. I don't have a service/parts manual handy. So I don't know what I am getting into.

I cannot recover the machine, so it will be an infield repair. I plan on getting some tarps under it so parts don't get lost. I imagine I'll have lots of things to look at when it starts being dis-assembled.

I guess it is time to start looking for shop and parts manuals too.

I appreciate the input, advice and thoughts on this thread I hijacked from the OP.

 

[riptides]

Oh, I went to messicks to get a diagram to look at. I always forget about that service.
Very nice, TIA.

Also, if I get it back together, I'll pull the left side for inspection, because I don't like a wheel going one way when I am going another. Thank goodness I was not by the creek bed, I just finished that swath......

FEL low to the ground, ROPS up and seatbelt on. Still freaked me out.

 

[brain55]

I just got in from the back, with the same catastophic failure. Identical is the word.
Will be calling the dealer in the AM. I think I just rolled 440 hours.

Very disappointed.

If you use the parts for a B21 you will not have this problem again. I have made this repair countless times, and once the axles are upgraded they do not break again. If you continue to replace them with the same parts they will continue to break. Not everybody has this problem, but for those that do, this is the solution!

Brian

 

[riptides]

I closed this out with parts for under 300.00 dollars. I kept the original part as opposed to upgrading.

Thanks to equipment diagrams and the dealer which/who walked me through it.

I returned to mowing duties and did a hay wagon pull this past w/e.

 

[slowzuki]

Next time you should upgrade the parts. I've not had any troubles with my L5030 and use it much harder than you are describing. I have 3 times the hours too. I can't imagine censoring the lifting with my loader beyond just what the hydraulics are capable of. I do drive sensibly when the bucket is loaded though.