Front Axle Slipping/4WD Slipping - Nortrac 254

[430488]

2008 Nortrac 254. I was admittedly overtasking my tractor digging with the FEL in 4wd when I heard a "clunk" and lost my 4WD. It was my own fault but now I need to figure what is wrong. I need some help. Here is what I have done. I was hoping it was the drive shaft or a universal slipping. But it's not.

1. Jacked up all four wheels
   1. No clunking, clanking, or clicking anywhere.
   2. Tractor shifts in and out 4WD
   3. In 4WD and tractor running in gear all four wheels are spinning
   4. In 4WD with tractor running and in gear, I can stop both front wheels from spinning with my hands
      1. Rear wheels continue to spin
      2. The front drive shaft continues to spin and looking at the front drive shaft connection to the front differential, with the metal sleeve cover pulled back, everything I can see continues to spin.
      3. If I remove my hands from the front wheels, they begin spinning again

It makes me think that something internally in the front axle is broken or teeth are worn away. Maybe in the center of the axle where power gets transmitted to the front wheels from the drive shaft? It confuses me that both front wheels spin in 4wd and being able to stop them by hand, like everything is slipping.

I need some advice on next steps. I think I need to get inside the front differential but I am not sure the best approach. Take off the rear support right behind the differential or the front differential support or start somewhere else? Any idea where or what the probable failure is? I do have a good diagram but still where to attack it from where I can inspect was is happening inside.

I appreciate any insight in advance!

 

[tshep]

I don't know your machine, but that is the way an open (un-special) differential works.
The question is: can you (safely) stop both wheels at the same time?
(And do you happen to KNOW there is no differential action in the transmission case.)

You did not tell us how you determined (tested before jacking) you lost 4WD.

 

[430488]

Thanks. With all 4 wheels on the ground, the fronts are not spinning in 4WD. I was stuck in dirt at the time of the original clunk and the 4wd was not working. Yes, in the air I can stop both tires from spinning with my hands. If I release them they start turning again. I don't think there is any differential action in the transmission case. The 4WD is either engaged or not engaged.

 

[piper184]

With the engine off and the tractor in gear and in 4WD, jack up one front wheel and try to spin it by hand. It should not turn.
If it does turn, does the front drive shaft turn?
With the engine off and the tractor in gear and in 4WD, with all 4 wheels on the ground, can you turn the front drive shaft by hand or perhaps with a screw driver for a little leverage?

 

[430488]

With the engine off and the tractor in gear and in 4WD, jack up one front wheel and try to spin it by hand. It should not turn.
If it does turn, does the front drive shaft turn?
With the engine off and the tractor in gear and in 4WD, with all 4 wheels on the ground, can you turn the front drive shaft by hand or perhaps with a screw driver for a little leverage?

Thanks. To answer your questions… either front wheel raised in 4wd and in gear either front wheel will turn. The drive shaft will “jump” but does not turn.
The front drive shaft will not turn with all 4 wheels on the ground.

 

[piper184]

In 4wd and in gear and only one front tire in the air, nothing should turn. If both front tires are in the air, rotating one should make the other one turn the other direction and the drive shaft should not turn.
The driveshaft does not use a cross type U-joint but rather a CV type using a series of balls inside a housing. The parts diagram for my Jinma 284 shows this same set up at both ends of the drive shaft. In your case, I would suspect the front joint. If the front one were good and the back one was bad, the shaft would turn. I would take the driveshaft off and make sure all is well there. I have never done that, but as I understand it they are a bit of a bear to get the balls all lined up when putting back together.

Once you have the driveshaft off, you will be able to do some additional wheel turning to see if the front differential is working properly. Get both wheels in the air and spin things watch, feel and listen to make sure all is running free. Hold one wheel and spin the other, and the input shaft (pinion) should spin. Same with the other wheel. Then both wheels free and hold the pinion, and the other wheel should rotate in opposite direction of spun wheel. Both wheels on the ground and the pinion should not spin except for backlash of the gears. If the differential fails any of these tests, you will need to take it apart. Best if you can get the axle away from the frame enough to remove the top cover and have a look inside. If not, with the drive shaft off you should be able to block the frame up and just unbolt the pivot carrier and then the pinion carrier to have a look in from the back side. This will be a smaller hole and may not have as much view as taking off the top cover.

Please let us know how you make out and take plenty of pictures as you go. It will help you at re-assembly time and if you post them here it will help someone else in the future. As always, best of luck and keep asking questions.

 

[430488]

Appreciate the advice piper184. I don’t think it is in the drive shaft but I guess it is possible.

The popular break, behind the drive shaft engagement balls, seems to be an axle shaft. With a broken shaft wouldn’t you still have power being sent to the unbroken side?

 

[Bob Rooks]

With a broken shaft wouldn’t you still have power being sent to the unbroken side?

Nope. Not a limited slip differential.

 

[piper184]

If an axle shaft is broken cleanly then the unbroken wheel would likely spin if it were jacked up and free to do so, but the moment you put a load on that wheel it would stop and all the input power would just go to the broken axle. Two things I can think of that would cause one wheel to have power but not the other.

A broken axle that is not a clean shear, but jagged or at a slight angle. Each revolution the two stubs would grab and rotate together until something gave enough to let them slip. This would cause a jerking motion to the broken side wheel.

Broken or otherwise damaged spider gear assembly that could allow the differential to "lock up" one side and let the other spin more or less freely.

Still, I would start by taking the drive shaft off and doing the tests I listed above. Even if it is fine, you will have to take it off to work on the differential anyway, so it won't be a wasted effort. Unless you can get the top cover off without removing anything else.

Have you drained the fluid out of both sides? any debris or did it come out clean?

Do you have (or have access to) a bore scope that you could maybe snake in through the filler or breather plugs?

 

[430488]

So I had time today to dig into the tractor It was pretty easy to remove the front axle. Four big bolts. Two in front of the differential and two behind. Disconnect the steering knuckle on the left side and two people can roll the axle out. I popped the cover on top of the axle and quickly saw the 6 bolts that hold the ring gear onto carrier were all sheared. Unfortunately I had to disassemble the whole differential to get the ring gear out. Next weekend I will work on drilling out the broken bolts and getting it back together. Not an expensive repair but a little time consuming.