B7100HST Front Drive Shaft Boot/Pipe

KJINTF · Aug 24, 2011

Hi,
Sure could use some help - parts are getting expensive
The rubber boot and pipe assembly that covers the front drive shaft self destructed for the second time in 6 months. I replaced the brass bushing and boot about 6 months ago. Removed the shaft by punching out the roll pins, cleaned and greased the shaft where the bushing rides and added some oil to the front "U" joint assembly. Yesterday I found the pipe covering the shaft had broken at the rubber boot, the rubber boot was destroyed.

Is there anything special that I need to do / check in order to stop this from happening again?

beemer530 · Aug 25, 2011

Please correct me if I'm wrong, but I don't think the u-joint should be submerged in oil. All the u-joints I have had experience with either have grease nipples or are factory lubed and sealed. I thought the tube and boot were just to protect the u-joint.

beemer

KJINTF · Aug 25, 2011

Not 100% sure either
Last time I took it apart there was about a cup of 90w oil in the metal boot
The U joints were in oil
The shaft they connect to at the differential has on open bearing so I would guess the oil came from the differential
But it's just a guess

Still wondering why the "fix" lasted only 6 months when the factory install lasted 20 years or more

beemer530 · Aug 25, 2011

I bought my B8200 not running and am tearing the engine down now. When I separated my driveshaft I found some water in there and the u-joint has external rust.

I checked my exploded parts diagrams and there is an oil seal on the transmission end of the tube and also one by the front differential bearing and shaft input. So You got me which is right at this point. Yesterday I got a PDF workshop manual recently made available by Kubota and will ck it later to see if in mentions refilling this tube.

300zx · Aug 26, 2011

I have had my son's B6100 apart also. It had a small amount of oil in it which I think leaked through the front differential seal. Vic has said in previous posts that you do not add oil to this joint because the u-joint has sealed bearings. Also, the manual does not call for any maintenance in this area. I know it is confusing because of the small plugs that look like fill and drain plugs, but my only conclusion is that they are used to vent and drain any excess oil that might collect from a leaking differential seal. You can search for the previous discussions about 3 months ago. Here is how my son's joint looked apart and the pan shows the amount of oil that had collected in the can:

The problem we were having is that the white bushing and seal at the top/left of the tube that covers the drive shaft had slipped out of the tube. I had to disassemble the drive shaft at the u-joint to get the tube off and reseat the busing and seal.

My suggestion is to clean up the boot and can and re-install it. Make sure the shaft where the upper seal and bushing ride is clean, smooth and lubricated. That is all I did and it has stayed in place so far.

Good luck,
John

KJINTF · Aug 26, 2011

That drive shaft housing looks very similiar to my B7100

I see you replaced the stock hose clamp with a standard screw driven one - right there at that exact location is where mine broke again after only 6 months of service. The metal tube actually broke in half at that location the rubber cover also self destructed. The oil seal and brass bushing at the top side of the pipe are in great shape slip and slide as they should. Like yours I had a small amount of oil in the metal housing and found no mention of it in any of the factory shop manuals. Kubota wants $85.00 for that metal housing - I will weld mine back together it was cracked at the weld seam on the top side.

I did notice the front tires were flopping around a lot when in 4wheel drive on a steep hill. Checked the steering it all felt tight. How is the front differential connected to the tractor chassis. Looks as if mine has only the one swivel connection with one large bolt.

beemer530 · Aug 26, 2011

A single pivot in the middle is correct. As for as the drain and fill ports, I believe they are separate on the 4WD
beemer

300zx · Aug 27, 2011

I am amazed that it failed that way. The only thing I can think of is that the brass bushing and seal at the top bound up on the drive shaft, but I can't imagine how. It may be worth your while to replace the brass bushing and seal with the white nylon one and seal, like you see on the B6100. I just went to look at my B7100, but I couldn't see mine to determine if it was brass or nylon. I was thinking about this last night, I believe the tube is designed just to prevent grass and debri from twisting up on the drive shaft, so the bushing at the top does not need to be tight at all. I think your repair sounds logical to me.

As for the front wheels flopping around in 4WD, I don't know what to tell you unless the pivot pin is worn or there is a problem in the front wheel steering u-joints at the end of the axles. You may want to lift up the front end and try to figure out where the looseness is.

Good Luck,
John

KJINTF · Aug 28, 2011

Thanks John

As soon as I receive the parts, ordered them from Orange a week or more ago
Will get the tractor up on the hoist and post a few pictures
Sure is nice to have a 4 post 12K lb hoist - could get the old Class C 24ft Motor home up there, but not the new larger Class A - O well it still works great for the tractors and Jeeps
A few days ago when I crawled under the tractor I checked the brass ring and oil seal both in great shape and slip on the shaft like a hot knife into butter
Sure hope I can figire what caused the problem this time

Ken

beemer530 · Aug 28, 2011

After sleeping on your problem, maybe the focus should be on your description of "front wheels flopping around" If you are describing jerkiness (not sure if that's a word or not (hehe) in rotation of the front wheels or drive line while pulling under power, it could be coming from the front differential or axle. If it was in the pinion gear and shaft area it could cause premature damage to the output bushing/bearing of the pinion shaft which could cause the u-joint to tear the boot from the inside.
If your front axle is like mine there are no u-joint, or even the stronger constant velocity joints, at the wheels. It's all done with gears at each end of the axle. I bet it's hard to break as long as fluids are maintained and front tire/wheel size isn't changed.

beemer

KJINTF · Aug 28, 2011

Thanks Beemer

I was thinking along the same lines - there must be something releated to the flopping of the tires they never did that much flopping around before.
I rememebr some strange crunching noises a few weeks back while under a very heavy uphill load low range and in 4wd.

When I get the parts I will take a closer look and post some pictures

Not sure how the U Joint could move far enough to destroy the rubber cover and pipe from the inside but anything is possible. Similiar to yours mine has only a reduction gear at the tire end of the differential / axle.

CAE · Jan 16, 2012

I was using the search forum and found this post, excellent by the way!
When I found my bushing out of the pipe I took a look at the front driveshaft.
The yoke on the transmission wobbles badly, I'm hoping that the shaft is O.K.
since it is harder than the yoke. So it's time to pull it all apart and replace what is worn, maybe the yokes and joints etc.
From the pictures 300zx posted it looks as if you have to start disassembling from the front axle back to the transmission?
Any tips would be greatly appreciated!
Thanks CAE

KJINTF · Jan 16, 2012

Sorry to say mine turned out a whole lot worse than the simple front shaft seal. As you can see the frame assembly that is bolted to the block broke in half thus the front axle was hanging in the wind. Ended up welding it back together and replacing parts all is good now.

300zx · Jan 16, 2012

CAE said:
I was using the search forum and found this post, excellent by the way!
When I found my bushing out of the pipe I took a look at the front driveshaft.
The yoke on the transmission wobbles badly, I'm hoping that the shaft is O.K.
since it is harder than the yoke. So it's time to pull it all apart and replace what is worn, maybe the yokes and joints etc.
From the pictures 300zx posted it looks as if you have to start disassembling from the front axle back to the transmission?
Any tips would be greatly appreciated!
Thanks CAE

CAE, it is not a bad job to disconnect the drive shaft. Just loosen the clamp on the front part of the boot and slide the tube with the boot back up the shaft out of the way. Then remover the cover off of the u-joint (three bolts). Mine had oil in it that had leaked through the seal from the front differential, so you may want to put a pan under it when you remove it. Once you slip the cover back, knock the roll pin out of the front of the u-joint. Once the u-joint is loose, you can slide it back off of the differential shaft and then off of the drive shaft splines as well as the cover, boot and tube. Mine had a nylon bushing with a seal on the upper end that had come out of the tube letting it rattle on the drive shaft. I just knocked the bushing back into the end of the tube with the seal in place, cleaned up and lubed the drive shaft so I could easily slide the tube with the bushing and seal back in place and reassembled the u-joint and cover. It is all still in place. I don't know what else you will find if your u-joint and input shaft is wobbling in the front differential. Keep us informed on what you find. KJINTF's broken frame looked rough.

Good luck, John

CAE · Jan 16, 2012

Thanks for the responses, it does help alot.
KJINF that was quiet a fix you made, I'll take a longer look at mine while I'm underneath.
300zx thanks for the order of disassembly, I need to find out what has to be replaced.
Off topic a bit your post on you B748 was excellent, very nice job, one of the other issues I need to address, we get alot of snow from time to time here at 7500ft. elevation.
Thanks, CAE

Bluegill · Jan 16, 2012

Just a reminder folks, grease the front axle pivot points (mounts) often. If the front-end gets too sloppy (like the broken one above), stuff is goin to wear out, break and/or fly apart. I just spent over $1000 on our L3750 because of this problem.

hodge · Jan 16, 2012

Is it me, or does it seem like these broken pivot points happen mostly on loader-equipped tractors?

Bluegill · Jan 16, 2012

hodge said:
Is it me, or does it seem like these broken pivot points happen mostly on loader-equipped tractors?

Lot of extra weight on that front end with a loader.

KJINTF · Jan 16, 2012

I believe you are correct the FEL is almost certain to have helped this mess along. I had been carrying hundreds of buckets of rocks up a 4wd trail in the back yard over several years. I did notice the way the frame assembly came from the factory, kind of cheaply built by bending the edges over and welding them only at the ends. Two laminated plates made into one piece. You can sort of see on the cleaned up shot what I am talking about. Hoping it will go another 25 years now that it's all fixed up

Ken

CAE · Jan 17, 2012

After seeing KJINTF posts on his repair I took a look at my crossmember where the centerpin holds the front axle in place.
I can move my front axle forward and backward on the centerpin between the gussets, how much play should I have?
Thanks, CAE

B7100HST Front Drive Shaft Boot/Pipe

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