6340 Broken rear axle???

[cbislander]

Hi there,
This is my first post on here. I've had my 6340 for a little over a year. This winter it's been an absolute dog on the ice and coming up the hill on our driveway. No traction at all. The front wheels will be spinning and the left rear wheel will be digging a hole. I thought maybe the brake might be sticking on on the right side so I jacked it uo on that side to check, but the wheel on that side just spins freely by hand even with the tractor in gear. I just got stuck in the snow with both front wheels spinning and neither rear wheel turning.
Could I have a broken axle on that side? Or a failed diff? Or something sheared in the final drive? Any help would be appreciated.
Thanks

 

[Renze]

No just a selflocking front axle diff in the front axle and an open diff in the rear. Use the difflock pedal.

 

[cbislander]

With an open rear diff, at least 1 rear wheel would be turning, no? In this case I was stuck in snow covered mud with both front wheels spinning and neither rear wheel turning. And the diff lock does nothing, though I suspected that it was faulty for the last little while.

 

[Renze]

Ok.

On the 7745 and 63/7340 sometimes the rivets of the crown wheel sheared. Replacement can be done with low head inner hex head screws from the top, when the 3pt hitch cover is removed.

 

[cbislander]

Ok, that's pretty good news if that's what the problem is. It sounds likely.
Do you think they sheared in those models because they only used rivets in those models or did Zetor use rivets in other models as well?
And could this damage have occurred from applying the diff lock while the wheels were turning?
Thanks so much for the info! And happy new year!

 

[Renze]

Riveted crown wheels are pretty common in many diffs. Just the 7745 and its successors 6340/7340 sometimes sheared them off.

Dont use 12.9 bolts, they are too brittle to take any impact. 10.9 is the best bolt for high impact fastening, thats why we use them on slew rings for excavators. Ive been told inner hex low heads can just sit there without touching anything.

Assemble them with the prescribed torque, so they also hold together by friction. I'd use locktite between the flanges too.

A properly torqued down bolt is pre-stressed so any load applied, still doesnt change the net stress, which means cycle loading is lower and the fatigue is lower..

 

[cbislander]

Ok great!
Is it a big job to access the crown ring through the 3 pt hitch cover plate? Does the cab have to be removed from the tractor, or is there some access hatch in the floor by chance? Would it be almost as much work as removing the final drives to get at it that way? I need to do some brake work anyway.
Thanks again for your help !

 

[Renze]

Copied and pasted from the recent 7745 thread:

Remove D-M-P lever knob
Remove rear lower cover with some M8 bolts
undo the bolts of the cab floor (M8 bolts)
Also those on the front lip of the part on which the seat rests

Push the upper part of cab floor up, and tie the weight adjustment knob of the seat, tight against the steering wheel with baler twine, this will give you enough room to work.

To lift the 3pt lift cover an engine hoist is preferred, but you might try putting a piece of wood over the mudguards and use a comealong to lift it up. Dont forget to remove the top link backet as it connects the lift cover with the diff housing



....you might as well take a look first by dropping the pump plate (on which no pump is mounted in the 6340 as it has an engine driven pump) and look inside.

 

[cbislander]

I'm glad you mentioned that cover on the bottom. It was a lot easier to take that off and look at the diff than it would have been to take the 3 pt cover off.

After doing that though, I can see nothing wrong with the diff or the rivets. I did find a circlip and a washer sitting loose on the cover plate. No big chunks but some small bits of metal.

I turned the wheel with the tractor jacked up on that side and I can the differential just kind of shudder once in a while as I turn the wheel by hand. Doesn't turn at all.

I'm just draining the reduction gear now and I'm going to take the cover plate off that to see if anything is obviously wrong in there.

Any more auggestions would be appreciated.

Thanks

 

[ixer0]

Hi

Sounds like a broken half shaft.

Mike

 

[cbislander]

Thanks for your help guys. Got it apart yesterday and it is a broken half shaft I guess you'd call it. The shaft that comes out of the diff and drives the reduction gear. It was sheared off about 5 inches from the end that goes in the diff. So I'm getting a new shaft ordered. Is there anything else I should replace as well?
Another question about the dry disk brakes. I had a heck of a time getting the brake housing off because of the threaded shaft that activates the brakes. I'm not sure what it's called but it sticks out too far for the brake housing to slip out of the main casing. I had to get the two circlips off and pry the 4 arms off of it. It wasn't easy and it's not gonna work for putting it back together. Does anyone know how this is supposed to be assembled?
Thanks again,
Adam

 

[ixer0]

Hi

That threaded rod will unscrew off the actuator. Put a couple of nuts on it and lock them tight together. It will unscrew.

Mike

 

[cbislander]

Oh great Mike! Thanks a lot.
So just loctite it when reassembling then?
Cheers,
Adam

 

[Renze]

Replace all oil seals you encountered onnyour way in. The stretching during disassembly of parts is often too much for 20 year old seals and they stretch.

Hmmm a broken halfshaft... ive uprooted trees with the 5245 with a frontloader on it and a rear bucket full of dirt as ballast and nothing happened.

Would this breakage be a mere incident, Mike ?

 

[ixer0]

Hi Renze,

I've changed 2 of those on Supers. One had the bolts round the portal come loose, the other was on road work with a big trailer.

Mike

 

[Renze]

Mike,

I've heard about the bolts coming loose. Thats why this flange (which was changed from 4011 M14 to M16 on the 7 series to M18x1.5 on the 10 series) eliminated in the Proxima, by using a one piece casting.

And road work with a heavy trailer, then flexing of the diff housing, and thereby misalignment is the cause. A local contractor broke several diff output shafts and final shafts on Ursus tractors with a single axle 14m3 injector tank, the importer tied an M36 threaded rod underneath the diff housing, pulling on the 3pt stabiliser consoles. Then the diff shaft was ok but the trumpet housing cracked or the wheel flange sheared off. 80 or 85mm halfshafts of UR2 or UR3 just dont suffice for todays six pot duties. The Ursus axle was rated 6500kg but it broke like matchsticks.

...But breaking rear axles on UR1 are very rare here.

 

[cbislander]

Thanks for the info Mike and Renzie! I'm waiting on a new halfshaft and seals and related bits to arrive so I can start reassembling.
I'm wondering if the original insult may have occurred before I got the tractor, and it finally twisted clear off after my brakes locked up on that side before the other as it has been doing.
In any case I need to sort out the brake locking issue. I have the dry disk brakes out now and they don't appear worn or dirty (balls and ramps). The discs don't seem excessively worn either. The slave cylinders were replaced by the previous owner a year ago. The brakes grab and sometimes lock on when applied. When they lock I need to reverse direction and they let go. There's no progressive braking. Do you guys know what the disk thickness should be so I can rule out worn disks?
Any other ideas what could be causing this?
Thanks,
Adam

 

[ixer0]

Hi,

Unfortunately it's a common problem on the dry disc system. All you can do is make sure there's no rust where the balls run along and coat them with a smear of copper grease. (Not too much so they don't attract the dust) If the balls look black or dull and not nice shiny chrome it would be worth changing them too, so they roll with no resistance.

Mike

 

[forterra9641]

you can use an angle grinder to cut some small stripes in the disc lining material, that was done with my 6340 to ease the aggressivness. i also found if you apply the brakes for 2-300 meters in 5 th gear willl make them smooth. seems like they ned to get a bit warm to work fine. if the tractor stood idle for a period the brakes where terrible. but when i heated them up abit they where smooth for as long as the tractor was in use that day. you can also change to the new style organic brake discs, but they are not so good but a lot smoother.

 

[cbislander]

So I have the tractor almost all back together. Happy day! I got a machine shop to drill and press out the axle from the brake hub and managed to save the hub, thankfully!
So just need get the wheel back on and the brake linkage and such and replace the fluid and hopefully it will be good as new and not a fwd tractor anymore!
Thanks guys for your help . After I get the brakes adjusted I'll report back on their operation.
Cheers,
Adam