Front differential problem on b21 - any one want to help an idoit out!?!

[Dawgbrain]

Front differential problem on b21 - any one want to help an idiot out!?!

I have late 90's (I think '97) Kubota B21 with front differential issues. Hopefully someone here can point me in the right direction. I am trying to trouble shoot a problem in the front differential and decide if it is something that I can repair on my own. I have good tools and generally good mechanical skills but I have never worked on a differential of any kind.

Here are the symptoms.

2wd
slight gear noises coming from front differential while moving forward or reverse

gear noises are louder when turning and loudest when turning left

noises are much louder when over concrete

the front wheels have locked several times. When this happens you can usually move 6 or 8 feet the opposite direction and they will turn only to lock again. They lock together, not just one at a time. After several shifts from 2wd to 4wd and moving forward and back they will release.

When I raise the wheels off the ground with the bucket and rotate one wheel by hand the opposite wheel turns the opposite direction (in 2wd). If I turn the wheel back and forth there is a little more slack in 2wd than in 4wd. I was surprised that there was any relationship between the front wheels at all in 2wd at all. Is this normal?

4wd

the noises are pretty much the same as 2wd but a little louder and I can feel them more (through the steering)

History

The tractor has about 1200 hours and has seen moderately heavy use. I have only owned it for the last 100 hours or so but I am not aware of it ever having any major issues. The maintenance has been kept fairly well up to date by both by me and the previous owner.
Prior to the current problems two things of note happened recently. First of all I let a friend use it to do some landscaping. He didn't realize it was a problem to leave it in 4wd on hard surfaces. He mostly just crossed his driveway with it (no turns or extensive operation). Secondly I ran it for about ｽ a day doing some clean up on my property. When I returned to the house I realized that one of the front tires was virtually flat. I am not sure how long I ran it this way or if it even matters.

So where do I start? Should I just jack it up and tear in? Are there any tricks to assembly/dissasembly. Any specialized tools needed? I have a good hyraulic press if I need to press any bearings or anything. Or is this the type project that I should hand over to someone with more experience?

Thanks in advance for your help!

 

[hill]

Check the oil. Use a gear oil if needed.

Check the wheel bearings. Initial check can be to get the wheels off the ground and try wiggling the tire, grabbing it at top and at bottom (not front and back) to see if the bearings are loose. If so, adjust them.

It's correct for one side to be turned opposite a wheel you turn, when both are off the ground.

If you have the manuals for your tractor there's plenty of useful and related info already available to you. If you don't have them I'm pretty sure the info is also available online in various sites.

Tractors are generally simpler than cars and trucks.

 

[dfkrug]

Well, DAWG, let's hope all your problems are in the front axle and diff,
and not it the range shift gearbox. If true, you can remove the whole
front axle assembly and fix it. If the latter, then you have to split the
tractor, and first remove the mainframe. loader, etc. Lots of work, and
more than on most compact tractors.

The gearbox, which includes forward/rev, 4x4/4x2, PTO, and ranges has
been known to have weaknesses on B21s.

First thing I would do is isolate the problem completely by removing the
MFWD driveshaft. Do that and see if you get the same symptoms. Let's
hope the 4x4 shifter fork/shaft is not to blame.

 

[638]

"When I raise the wheels off the ground with the bucket and rotate one wheel by hand the opposite wheel turns the opposite direction."

This is normal.

It sounds to me like you have broken a tooth off of one of the pinion gears. You may be able to isolate which side by jacking up the front end and turning each wheel back and forth just a little bit and notice how much play is in the gear. Then rotate the wheel just a little bit farther and repete the rocking motion. Do this on each side at least two times around on each side. If you don't find any position that has more slack than the other positions it could be a tooth off of the drive pinion in the differential. I would not drive it untill it is fixed because if the gear teeth come up end on end, it could split the gear case.

 

[dex3361]

Do you have a parts diagram? If not you can go to the index of Kubota books and down load a PDF. The numbers may not be the current part numbers but it will show you how it is put together.
INDEX OF KUBOTA BOOKS

 

[Dawgbrain]

Okay, you guys have definitely given me some direction. Thanks! I am going to clear a spot in my woodworking shop for it tonight and get hopefully get started investigating it deeper tomorrow night. Again, thanks for taking the time with all of your replies.

 

[slowzuki]

STOP DRIVING IT! Every foot you move is just costing you more money in parts.

Pop the low drain plugs on each housing near the tires, one side will likely have a bunch of metal flakes come out with the oil. Block it up and take apart this side, there are descriptions of how to do this on here. Big snap ring pliers are the only special tool. All the bearings will be ruined, and sounds like a gear will be missing a tooth but maybe not.

On mine the cage on a bearing fell apart and got mashed up going though the gears multiple times then contaiminated all the bearings. You need to clean everything really really well. New seals while you're in there. You shouldn't need a press, most Kubota's everything is slip fit. You may have spun a bearing, your budget will determine how you want to fix the damage to the surface the bearing spun on.

If you're really unlucky, the damage happened in the pinion area of the differential, but this isn't as common.