Throbbing in 4wd

[kiltedpiper98]

I have a BX2200, with about 250 hours on it that has run great for a while. I recently had a sheared roll in in the u-joint for the front drive shaft, and temporarily replaced in with various pieces of metal. Most of them ended up shearing off. I finally got around to replacing the roll pin with a new roll pin. However, now when in 4wd rolling straight or turning, the tractor throbs, or grabs, or surges forward. If I put it in 2wd, no problem. I greased the drive shaft at both ends. I checked the fluid and it is in the stick. It is a little darker than the hydo fluid. Any ideas?

Jim

 

[_RaT_]

I have a BX2200, with about 250 hours on it that has run great for a while. I recently had a sheared roll in in the u-joint for the front drive shaft, and temporarily replaced in with various pieces of metal. Most of them ended up shearing off. I finally got around to replacing the roll pin with a new roll pin. However, now when in 4wd rolling straight or turning, the tractor throbs, or grabs, or surges forward. If I put it in 2wd, no problem. I greased the drive shaft at both ends. I checked the fluid and it is in the stick. It is a little darker than the hydo fluid. Any ideas?

Jim

Sounds like too much difference in lead/lag with the tires. Are they stock, are they inflated correctly?

 

[DDM84]

It sounds to me like either the front axle or the drive shaft have been damaged in some way. Try removing the drive shaft and inspecting it for any damage as well as the couplers. Check out the output shaft on the trans and the input shaft on the front axle. See if they are loose or bound up tight in any way. You can also drive the tractor in 4wd with the drive shaft still off to see if the throbbing is coming from the transmission. It's some where to start. Let us know what you find.

By the way, what were you doing when the pin was sheared?

 

[leonz]

I have a BX2200, with about 250 hours on it that has run great for a while. I recently had a sheared roll in in the u-joint for the front drive shaft, and temporarily replaced in with various pieces of metal. Most of them ended up shearing off. I finally got around to replacing the roll pin with a new roll pin. However, now when in 4wd rolling straight or turning, the tractor throbs, or grabs, or surges forward. If I put it in 2wd, no problem. I greased the drive shaft at both ends. I checked the fluid and it is in the stick. It is a little darker than the hydo fluid. Any ideas?

Jim

where does the roll pin come into all this? I have never seen a roll pin in a drive shaft U joint?

Is the roll pin used to retain the yoke on the front axle if the axle has a stub shaft the the yoke slides into and the roll pin holds the yoke in place
by passing through the yoke and a hole in the axle stub shaft tha recieves the roll pin?

perhaps that is what you mean?

instead of a castle nut, Yoke, washer, O ring, and cotter pin?



Is the front drive shaft on that extends and retracts like most other drive shafts? does it have a grease fitting on the outer sleeve to actually grease the propeller shaft itself?


It seems that your U joints and propeller shaft are shot as it is binding and releasing in 4 wheel drive it happens with trucks a lot with adjustable cup and cone bearings that are tightened as they wear.

you may be dealing with a bad bearing in the front axle behind the yoke and possibly a bent shaft which is most likely as you continued to run it.


the front axle will have to be elevated to see if the drive train still binds when it is rotated. most likely you need 2 U joint bearings if they can be purchased separately. If the shaft is out balance twisted bent the least little bit you are SOL and hope the transmission and front axle bearings are still good as well as the shafts of the transmission and front axle as well as the transmission seal.


whoopsy:confused2:

 

[kennyd]

Sounds like too much difference in lead/lag with the tires. Are they stock, are they inflated correctly?

That would be my first guess also-tires.

 

[kiltedpiper98]

I will check the tires. As to what was happening when the pin sheared, I don't really know. I was mowing with the MMM in 4wd (hilly and a little wet, BX2000 is quite light and needs the 4wd to go uphill w/o spinning the back wheels). I heard a rhythmic thumping and looked under the chassis and ontop of the MMM was the 4wed drive shaft. The drive shaft is quite small and runs between a U joint at the frame where it ties into the shaft coming out of the transmission? under the seat. Then it slopes down to another U-joint coming out of the front diff. I searched the forum for the sheared pin problem and saw it seemed pretty common with the BX series. The front drive shaft U-joint pin is a castle pin? with a washer and cotter pin. The back shaft U-joint is a roll pin. I ordered a bag of them from the dealer. Yes the shaft slips in and out at the u-joint under the seat.

I disconnect the shaft at the front u-joint and ran the tractor in 4wd to check and it ran smooth. I also tried to watch (wife driving forward slowly while I watched) and didn't see anything that would indicate the driveshaft is bent or rubbing wrong on the u-joints. Also, I would think if the driveshaft was bent it would cause problems all the time, because it spins while driving even in 2wd. The release mechanism is in the transmission area, not at the front diff.

I will check tire pressure. I don't have a manual (on order), what should the fronts and backs be at?

 

[kiltedpiper98]

Also, could it be a front diff oil problem? When pick the front end off the ground in 2wd and rotate the tires, one turns forward and one backward (I am pretty sure this is normal). There does not seem to be any binding, but I can feel the gears engaging. If I pull the dipstick out and twist the tires the gears that I can see seem to pull the oil up over them.

 

[kiltedpiper98]

Oh, the tires are the grass master kind, and are stock sizes.

 

[Wacky]

Drain the fluid and check for excessive metal shavings.

 

[leonz]

about your tractor:

The oil level is fine

the front tires are supposed to spin like that as it is a limited slip differential so no worries there.
the propeller shaft spins all the time in 2 wheel drive otherwise the front and rear axles would be working against each other.

As the roll pin sheared and you did not immediately replace it with the proper roll pin and continued to use it, it has most likely lost one or more teeth in the spur gear in the front pumpkin.


The only way determine this is drain the oil out of the front axle and see if the oil has any metal chunks in it or if there is metal it will be stuck to the magnet if the drain plug has a magnet-the old kubotas from 30 years ago did have magnets anyway.


After you drain the gear oil you need to flush the front axle with some diesel fuel to remove any metal that may be left there and either remove the entire front axle and replace the differential or have your dealer do it.

As you have 250 hours on it it may be serviceable with the existing warranty.


leonz