I was digging today and made a push in low gear but hit some hard clay. The tractor came to an very abrupt stop with a loud pop/clink coming front under the seat. I backed up and the rear end was making a popping/clunking sound. Obviously something broke. When unloaded and moving forward or back the noise is not very noticable but when turning or under load its very loud. The HST, Transmission ( high, med and low) and the front drive seems to be working fine. If anyone may know what gave out it would be greatly appreciated. Thanks Scott
B21 rear end noise
- Thread starter scott77711
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Scott before you panic check your HST fluid level. There's another member on here that experienced a similar noise. Read your operators manual and see if it doesn't make a statement about being in the float position with the FEL when digging into a pile because it saves on wear and tear. The FEL standards attached to your frame probably slammed against the frame rails when you hit the hard clay. It sounds like its under your seat and pops really loud when you jam the bucket into a fixed object. All Kubota products are designed to go over relief pressure settings before you break a weldment. This is why I think you are okay. 
The front wheel drive is driven from a gear on the pinion shaft. If the front is still driving normally the problem will be after the pinion shaft. (crown gear, differential, either final drive, etc.) You can further pin it down by experimenting with the diff lock and each wheel brake. I don't know of any known weakness in there, but there would be extreme torque on all the components with a hoe on in low gear in excellent traction conditions! Somethings gotta give! seeing it is worse when you are turning I'd suspect the differential.
Ed
Ed
Thanks for the info. I really beleive it in the differencial after some further investigation. The initial popping noise game from the rear end. It continues to make the noise. Do you think that its not in the rear?
Two thoughts I'm looking at a May 97 sales brochure where the breakout force is rated at 1543 lbs about (700kg). I can't image hard clay has the tensil or compressive strength to shockload a rear differential. Were you spinning at near 2600 rpm cutting the clay? A shockload is all I can thing of would cause the axle side gears to explode. Blade a stump ( at your own risk ) and see if the rear wheels starting spinning without the popping noise. At that point you have ruled out a major problem in the rear differential IMHO.
You can do what you like but I wouldn't recommend stumping that machine and seeing how much rubber you can peel off! If there is something broken in there the next pop and snap may be a couple of gears finding their way out the bottom of the transmission!
I would lift the rear of the machine off the ground, put the range lever into a gear and rotate the rear wheels by hand. if they turn smoothly and the one rotates opposite to the other your diff is probably OK if there is any roughness or unusual noise you'll have to take it apart to see where. If it turns OK put the range lever into neutral, make sure it is out of 4 wheel drive, engage the diff lock and turn the wheels again. if you have an unusual noise now the problem is in the crown and pinion area ( broken gears, bolts broken on the crown gear, etc.) . with the diff lock engaged both rear wheels should turn the same direction.
I don't see where the breakout force of the loader would come into play. If you were cruising along and the bucket hit solid enough clay to stop the tractor dead you would generate some huge torque in there and something could break!
Ed
I would lift the rear of the machine off the ground, put the range lever into a gear and rotate the rear wheels by hand. if they turn smoothly and the one rotates opposite to the other your diff is probably OK if there is any roughness or unusual noise you'll have to take it apart to see where. If it turns OK put the range lever into neutral, make sure it is out of 4 wheel drive, engage the diff lock and turn the wheels again. if you have an unusual noise now the problem is in the crown and pinion area ( broken gears, bolts broken on the crown gear, etc.) . with the diff lock engaged both rear wheels should turn the same direction.
I don't see where the breakout force of the loader would come into play. If you were cruising along and the bucket hit solid enough clay to stop the tractor dead you would generate some huge torque in there and something could break!
Ed
One thing that will cause some popping and snapping on that vintage of B tractor is the wheel fitment to the hex axle. Check that the locking bolt is tight.
Hey Ed I don't think there's anything wrong in the diff. I don't have that WSM is there limited slip clutches in the third member housing or just a solid pin locking the spool in for lock up? Anyway a little wheel spinning against a stump to prove it will save a tear down. We don't know if he's got a shop, his skill level, etc. and those little B were pretty beefy ( considering the backlash and bearing preloads were set correctly at assembly) for clay to shock a tooth off or cause a spline to shear. If its already damaged one more definitive test will at least locate the area of failure. I don't want him to get hurt if he doesn't have a level concrete floor to jack her up with good stands to support her while spinning the wheels. We can't assume anything until Scott makes a move. You are spot on with your diag(x) with hand spinning for an open rear. Lets see what he does....
We don't know if he's got a shop, his skill level, etc. and those little B were pretty beefy ( considering the backlash and bearing preloads were set correctly at assembly) for clay to shock a tooth off or cause a spline to shear. If its already damaged one more definitive test will at least locate the area of failure. I don't want him to get hurt if he doesn't have a level concrete floor to jack her up with good stands to support her while spinning the wheels. We can't assume anything until Scott makes a move. You are spot on with your diag(x) with hand spinning for an open rear. Lets see what he does....
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Hi OB1
No limited slip clutches in any Kubota that I know of, they all use a sprag clutch which locks one pinion shaft to the carrier. That is a B21 so it likely has a backhoe on it, the best jack and stands system I ever saw for checking out the rear end. They ARE built very beefy in the back end, and as you say, provided they were set up properly from the factory, should have no problem. The problem is there IS a problem! Something is making the noise when the tractor is under load and/ or turning. I have no idea yet the condition of this machine or the amount and quality of maintenance that has been performed on it. But I don't want it to be further damaged if at all possible. I just repaired a transmission on a M125X a couple of weeks ago that shouldn't have failed either but it did! I wish the customer had brought it in when it first started making noise and not when it wouldn't move anymore, sure would have cost a lot less to fix! It started out with a failed $20 bearing and wound up with a $8000 dollar repair.
Ed
No limited slip clutches in any Kubota that I know of, they all use a sprag clutch which locks one pinion shaft to the carrier. That is a B21 so it likely has a backhoe on it, the best jack and stands system I ever saw for checking out the rear end. They ARE built very beefy in the back end, and as you say, provided they were set up properly from the factory, should have no problem. The problem is there IS a problem! Something is making the noise when the tractor is under load and/ or turning. I have no idea yet the condition of this machine or the amount and quality of maintenance that has been performed on it. But I don't want it to be further damaged if at all possible. I just repaired a transmission on a M125X a couple of weeks ago that shouldn't have failed either but it did! I wish the customer had brought it in when it first started making noise and not when it wouldn't move anymore, sure would have cost a lot less to fix! It started out with a failed $20 bearing and wound up with a $8000 dollar repair.
Ed
hey eserv,
I've got a similar problem i think you know with my back end of my b21 where it clicks under load and doesn't want to move and if you are driving you can hear a clucking noise under the seat.. is there an inspection plate i can quickly pop off and check out the diff or do i have to take off the trumpet housing?? thanks for any advice
I've got a similar problem i think you know with my back end of my b21 where it clicks under load and doesn't want to move and if you are driving you can hear a clucking noise under the seat.. is there an inspection plate i can quickly pop off and check out the diff or do i have to take off the trumpet housing?? thanks for any advice
You will have to remove the TPH housing. probably what you mean by "trumpet housing"! Some folks call it "the frog" around here! It's not that hard to remove but you cannot repair anything from there if it is broken, though you'd be able to see if the diff is OK. We have hardly any trouble with differentials in Kubotas but we do have some bearing failures. The problem could be in one of the final drives too. They are very simple to remove and check out. Kubota use a form of silicone instead of gaskets in most places so you don't even need to buy new gaskets!
Ed
Ed
pat331
New member
Equipment
L35, mower, bushhog, cement mixer, grader, boxblade, forks, posthole digger
I've been following this thread very closely because a similar experience w/ my L35. I can't say how close the B21 is to the L35. On my L35, I was pushing a tremendous load with it in 4WD with the backhoe on and fluid in all 4 tires. The obstacle wasn't moving, so I was hitting it when the final drive at the back of the transmission sheared of some teeth on two mating gears. Neither of the differentials were damaged. The tractor would not move except by pushing it around with the backhoe. I had to winch it on the trailer to take it to the dealer for repair. $2K later, it was fixed.
You are right pat331, the problem could be either or both final drives. They are simple spur gears so the load is concentrated on little more than one tooth!
The B21 and the L35 are similar in design and construction but the only part that will interchange between them is the oil!
Ed
The B21 and the L35 are similar in design and construction but the only part that will interchange between them is the oil!
Ed
Ed here's what I'm talking about; look at the attachments. These are Kubota LSD. I'm just not sure if the B series has them....it could be the source of the noise. These clutches are noise producers under a load with wheel slipping, this may be his noise.
Attachments
Hi OB1
The B series tractor isn't equipped with a limited slip front differential.The B21 also doesn't have a front differential lock, just a rear diff lock. The noise is coming from the rear of the tractor. The sound COULD telegraph up the drive shaft to the rear and sound like it's coming from the rear if it had a limited slip. also the limited slip only makes noise if you are turning or the diff is operating because of wheel-slip. the owner said his makes noise when under load, I assume even going straight, though I probably shouldn't have made that assumption!
Ed
The B series tractor isn't equipped with a limited slip front differential.The B21 also doesn't have a front differential lock, just a rear diff lock. The noise is coming from the rear of the tractor. The sound COULD telegraph up the drive shaft to the rear and sound like it's coming from the rear if it had a limited slip. also the limited slip only makes noise if you are turning or the diff is operating because of wheel-slip. the owner said his makes noise when under load, I assume even going straight, though I probably shouldn't have made that assumption!
Ed
Hi OB1
The LSD was introduced with the M40 series tractor and is standard equipment on the M7040dt. M8540 and M9540 tractors. The previous model M30 series tractors had a mechanical diff lock activated with a pedal on the floor. As far as I know this is the only application of a LSD on Kubota tractors.
The M___X series are using a hydraulic applied diff lock on both the front and rear differential.
Ed
The LSD was introduced with the M40 series tractor and is standard equipment on the M7040dt. M8540 and M9540 tractors. The previous model M30 series tractors had a mechanical diff lock activated with a pedal on the floor. As far as I know this is the only application of a LSD on Kubota tractors.
The M___X series are using a hydraulic applied diff lock on both the front and rear differential.
Ed
Thanks for all the info guys. I brought the unit into the dealer. Turns out the ring and pinion broke. Unfortunately it also cracked the case. That was probably from trying to trouble shoot the problem. I tried all of techniques you guys mentioned (short of the stump) and came to the conclusion that it was seriously broke. Using the backhoe outriggers is the fastest and safest way to lift the machine and of course supported by jack stands. Its going to cost close to $2K for the repairs. Maybe I should have bought a skid steer!!!
Hello Scott
Sorry to hear that the B21 was such a major! As regards whether you should have bought a Skid-steer, Well, $2000 is just a tune-up on one of those! We sell Gehl, and though they are very reliable machines, $3000 to $4000 repairs are all too common! I repair and rebuild the pumps and motors on them but most dealers just put new or rebuilts on them. Those things also wear out tires pretty quick and that will chew a big hole in $2000.
Ed
Sorry to hear that the B21 was such a major! As regards whether you should have bought a Skid-steer, Well, $2000 is just a tune-up on one of those! We sell Gehl, and though they are very reliable machines, $3000 to $4000 repairs are all too common! I repair and rebuild the pumps and motors on them but most dealers just put new or rebuilts on them. Those things also wear out tires pretty quick and that will chew a big hole in $2000.
Ed