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breaking teeth on gears in front axle on a john deere 855

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Howard Faunce
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2000-08-07          18597

I keep breaking teeth off on a gear in my front axle when digging dirt with my front bucket any reasons why and what to do to prevent it?

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breaking teeth on gears in front axle on a john deere 855

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Kenneth W Spriggs
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2000-08-08          18647

I have A JD 4600 with front wheel drive which constantly breaking the mounting bolts and wearing out the front tires. The front wheel drive on the John Deere tractors is a nightmare, they need more engineering ....

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breaking teeth on gears in front axle on a john deere 855

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Big Eddy
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2000-08-09          18673

Doesn't sound normal to me!
I've never had any problems, and am interested if either of you are using non-standard tires. If your tires are non-standard, then the front and back wheels will turn at different speeds and something has to slip or give.

Possible cause?

BigEddy
....

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breaking teeth on gears in front axle on a john deere 855

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DanaT
Join Date: Jun 1999
Posts: 138 Clay Center,Ks
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2000-08-09          18675

There has to be a reason for your problem!
Is the linkage going all the way in when the front end is locked in? (might be a dumb question but it's my first thought). Do you have the front locked in on hard surfaces? How many times has this happened? I've haven't had any trouble like this with mine and I dig deep hole in the ground alot. I would like to know reason as well. ....

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breaking teeth on gears in front axle on a john deere 855

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Murf
Join Date: Dec 1999
Posts: 7249 Toronto Area, Ontario, Canada
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2000-08-09          18676

If I had to guess (which is all I can do with so little info.) I would say that it was caused by the front wheels biting in, the back wheels slipping a little, because the machine is off-balance by the loader weight, and so the front-end gears are the weakest point. If the front tires are the only thing getting traction and the front wheels spin then connect, on a rock or gravel for instances, then as previously stated, something has to give. Best of luck. ....

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breaking teeth on gears in front axle on a john deere 855

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Howard Faunce
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2000-08-09          18679

I have broken the gears on the front end of my 855 twice on the right side and once on the left side
The front end is locking in everytime and it always happen when trying to dig with the front bucket and the tractor is on dirt
Yes I have the same size tires that came on it so I don't see how that would be the problem
I would have to say also the rear tires are not slipping either
Thanks for the suggestions but I don't think that this is the problem ....

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breaking teeth on gears in front axle on a john deere 855

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DanaT
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2000-08-10          18714

Howard, Do you use a rear weight while digging? ....

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breaking teeth on gears in front axle on a john deere 855

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Howard Faunce
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2000-08-10          18715

yes I have my rear tires filled with calcium
I have had them filled since new with no problems till now
I bought my 855 new in 1987 and I have about 890 hours on it now
I know one thing for sure is that it costs alot to fix it was $180.00 just for the parts I'm just lucky I can do the repairs myself ....

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breaking teeth on gears in front axle on a john deere 855

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Roger L.
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2000-08-10          18716

Howard, about the only thing I can think of is that maybe the 4wd lever is staying stuck in 4wd.....so that even when you shift to 2wd for traveling, it is actually staying in 4wd. With a full bucket and good traction, staying in 4wd when traveling would wind up the drivetrain something fierce - and could break the front gears if they are the weak point in the driveline. ....

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breaking teeth on gears in front axle on a john deere 855

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Howard Faunce
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2000-08-10          18718

Roger
thanks for the suggestion but I have gone over every thing there is to adjust and checked to make sure everything is adjusted the right way according to the shop book the gears that are breaking always turn no matter if its in 4wd or not so I don,t think that is the answer thanks any way ....

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breaking teeth on gears in front axle on a john deere 855

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Roger L.
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2000-08-10          18719

Howard, I am not talking about something that can be adjusted, it would be a matter of on internal part failing. In the case that I am talking about, when you move the 4wd lever, it moves a shifting fork and shoe that forces an internally splined gear to slide along a shaft. This is the gear that engages the MFWD driveshaft and sends power to the front axle. If the hand lever is not sliding this gear along the shaft properly, then your tractor will be in 4wd regardless of the position of the lever. Leaving a tractor in 4wd with the front end loaded will definitely cause drive train failure.
Aw shucks, Howard....now you've gone and got me interested. I know you say that the gears are always turning whether or not it is in 4wd - I agree. But the gear sets are not always stressed. That depends on whether it is in 4wd or not.
Which gear set is it that is failing? I guess I had better describe the 855 MFWD axle for anyone who doesn't know and who hasn't fallen asleep yet :-)
The JD 855 MFWD is a slight variation on the typical Yanmar-developed mechanical front axle. The axle is driven in the center with an "almost standard" pinion and ring gear type differential. The only unusual feature is that the pinion shaft is NOT driven directly by the drive shaft, but is driven by a set of spur gears set in a casting on top of the pumpkin. One of these spur gears are driven by the front drive shaft and its mate in turn drives the pinion shaft. (ratio 14/11 by an old parts book from my library...odd... that gears it up, not down as one would expect)
The rest of the front axle is the typical YM-type bevel gear front drive. Looking at one side: a stub axle off of the planetary terminates in a bevel gear that drives the top of a bevel gear tower. The vertical shaft in the bevel gear tower allows for steering rotation on each wheel. The lower end of the tower contains a third bevel gear pinned to the vertical shaft which acts as the pinion for a ring gear mounted on the inner face of the wheel axle spindle. (AH! that is where the extra gear reduction lives....in the wheel spindle ring gear!) If you can make that out without a picture you are a better man than I! Let me reiterate in synopsis: The basic picture is that there are a set of spur gears into the differential. The differential itself has a pinion driving a ring gear. There are the typical planetary gears (spiders) driving two stub axles and then there is a matched set of bevel gears out at the top of each tower and a bevel gear and ring gear driving each wheel.
Howard, if you could tell me which of these gear sets is breaking and how, then we can get to work on a reason why.
....

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breaking teeth on gears in front axle on a john deere 855

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Howard Faunce
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2000-08-11          18749

Roger thanks for your suggestions but still not sure
The gears that keep breaking are the top spindle bevel drive gear and the spindle bevel imput gear it seems though that either a snap rink is breaking or a spacer is breaking ang its getting into the gears which in turn is breaking the gears ....

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breaking teeth on gears in front axle on a john deere 855

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Roger L.
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2000-08-13          18817

Howard, that certainly is not the gearset that I was expecting to break. I agree with you that those gears turn in 4wd or not, and although any front axle gets hit with windup stress if the machine is driven loaded in 4wd, it should be able to take a moderate amount of this.
Looking at the exploded diagram, I cannot tell if there appears to be a snap ring positioned where it could drop into the teeth. This is because my parts book and service manual cannot agrre if there are two ball bearings separated by a snap ring above the driven gear on the vertical tower shaft - or if there is only one ball bearing with the snap ring between it and the bevel gear. Which way is yours put together??
Another odd thing is that The service manual does not give any shimming instructions for the bevel gear engagement. Nor does the parts book show any shims. When Yanmar puts a similar axle on their own tractors, they put a lot of effort into shimmming these same fits. Odd that they would do it differently for JD. As far as I can see, the bevel gears on the JD are free to float laterally along their gear shafts a small amount. Is this true?
I have not heard of other 855s having a similar problem - have you? Without some more detective work, this is not going to be easy. I'll confess that I don't have a ready answer.
....

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breaking teeth on gears in front axle on a john deere 855

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Anthony M. Parente
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2000-08-21          19045

The tractor must be operated with a backhoe or ballast box to offset the load on the front axle when using a loader. All tractors are designed so that approximately 70% of the tractor weight is on the rear wheels. I have used my JD755 B/L and have never had any problems. I recently moved approximately 140 tons of shale a distance of 100 yards. The limiting factor was the lifting capacity of the #70 Loader.
I hope this helps.

Tony,
....

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breaking teeth on gears in front axle on a john deere 855

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Stan_McC
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2000-09-12          19768

As a former JD Consumer Products mechanic, I've had to rebuild several 55 series front ends. From what I have seen, it appears that when using the loader, people inadvertently end up with the front wheels off the ground at times. After noticing this, they lower the wheels back onto the ground while still trying to dig, sometimes jamming the front wheels back to the ground. The proof is the damage done to the snap ring groove for the bearings in the knuckle casting. If you take a close look at the design of the axle pivot area, you'll notice that the tractor is supported by the short vertical stub drive shaft, which is not a very good design in my opinion. I owned a 655 with loader and had oversize tires on it and with over 560 hours & no failure, it's because I was careful not to drop the front wheels on the ground, especially when trying to dig, and I worked the tractor well above the limits that Deere had in mind for it. ....

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breaking teeth on gears in front axle on a john deere 855

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n77wnn
Join Date: Mar 2012
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2012-03-15          182771

I have herd this from many JD machanics, in some cases It may be true however, no all cases I have a 855 and it seams that every year I have to change the gears in the left side some people it's the right for me its the left. If there was a race team for these tractors I could work on the pit crew because i'm so fast at changing out these gears, back to the point, the last two times the gears failed the loader was not even installed, what i was doing is pulling in soft dirt, and the other time I was pushing snow with a blade. This is nothing but a poor design, when you remove the gears you can see the gears do not mesh properly and there is no available shims for this application. not all 855's have this problem I know someone that has one, and has had no trouble, this tells me it's a casting flaw that John Deere had to be aware of and failed to own up to it, so we the consumer gets it in the end (and I mean end) ....

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breaking teeth on gears in front axle on a john deere 855

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Murf
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2012-03-16          182777

Welcome to the forum n77wnn.

Don't be surprised if you don't get much interest in the reply though, the thread was last active 12 years ago now.



Best of luck. ....

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breaking teeth on gears in front axle on a john deere 855

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JD-855-in-WI
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2012-03-24          182853

Interesting enough I just brought mine back from the dealer. I had a seal out in axle stub and a bearing and a broken gear tooth. The bearing cage failed, allowing the balls to all work around toward one side, wearing the seal, the shaft and shifting the gear alignment. This was on the left, rebuilt the right about 5 years ago. Now both sides have been sleeved where the seal has worn the shaft. Yes the gear faces can and should be shimmed for proper tooth alignment/engagement; if not the tooth faces will not mesh properly and can result in worn or snapped teeth. We used to use lamp black and orange die on the gears to check interfaces. Each cast hub is a little different and each finished casting ends up bored just a little different too. I see you’ve been doing them yourself, check with a JD mechanic and see if he’ll show you how to use the shim sets to adjust gear engagement. I probably did mine in last season with the backhoe, might say I was a little rough on it. But it’s still a good tractor with lots of life to go…… ....

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