L4400 cracked rear hubs

john_bud · Jan 17, 2013

I'll second the cause being loose lug nuts. but if when loaned out, the inexperienced users didn't set the stabilizers and dug out at 90degrees, that will crack the rims.

taborekle · Jan 18, 2013

Since these are fluid filled tires (and rims), I have to wonder if there was not enough air left in the tire.

Gary Fowler · Jan 20, 2013

CptTrog said:
Folks, sorry if this is a duplicate question, but the forum search engine is simply not helping me find any info. I know it's been addressed somewhere here.
Kabota L4400 rear hubs are spiderwebbing at the lugs. (Cheap steel or bad design?? Or maybe it's me.) I've purchased new hubs to replace the old ones. Here's my question:
Should I try to reinforce the new hubs somehow prior to installation? I'm using a backhoe attachment A LOT in very rocky terrain here in Virginia. Also operating on some pretty hairy grades when mowing or box blading. Also have all four tires filled with antifreeze.I've considered having a local welding shop cut and drill two rings for me from 1/4 steel and weld them to the outter surface of the new hubs.

Any feedback? Thanks!

I have a B26 and the books says that with the backhoe installed, rears should contain air only. That said, I would more suspect that your problem stemmed from loose lug bolts which is generally the cause of rim failure. Do you have a flat washer then a lock washer on each lug bolt? That is what it should have so the pressure is spread over a larger area.
Rather than weld in a reinforcing plate, put on an extra washer that is heavier and bigger than the factory one AND keep the lug bolts checked and tight. By putting a washer that is thicker and as big as it will fit in the bolt circle, you will spread the load over a wider area of the rim. The second washer would then spread the bolt head torque over a larger area on the bottom washer (think pyramid with the bolt head at the top and the bottom of the pyramid against the rim.)
You could likely fix those rims by grinding out the cracks, welding them up and then installing a thicker plate for reinforcement. Keep them for spares. Maybe put tires on them and put air in one set of tires and rims and water in another. Swap them out when using the backhoe so you have non ballasted tires then although I think the reason Kubota recommends no ballast with the backhoe is to keep the excess weight off the stabilizers and it has no effect on the tractor or rims. Just my opinion.

Edit: Looks like the consensus is LOOSE LUG BOLTS. I still like the addition of thicker flat washers against the rim to spread the load a bit. The factory washers on my B26 are pretty thin. A heavy washer in grade 8 material might be the ticket.

CptTrog · Jan 21, 2013

I tend to agree, Gary. Thanks for the suggestion about thicker/multiple washers. I believe that will likely help the situation tremendously.

sixdogs · Jan 21, 2013

CptTrog said:
I tend to agree, Gary. Thanks for the suggestion about thicker/multiple washers. I believe that will likely help the situation tremendously.

Agreed...great idea Gary.
One metric washer as opposed to two likely better since two increases opportunith for flex action. Also note your tires are probably overloaded to begin with so take it easy or lighten the load.

ballencd · Jan 26, 2013

I have a L35 with the same issue although the wheels are not two piece and I cannot afford to replace the wheels. Can I make a ring and weld it to the hub and run the lugs thru both the old wheel and the ring? I tried to attach some phots but could not get the app to work. ???? Charlie

dfkrug · Jan 26, 2013

ballencd said:
I have a L35 with the same issue although the wheels are not two piece and I
cannot afford to replace the wheels. Can I make a ring and weld it to the hub and run the lugs thru both
the old wheel and the ring?

I am surprised to see you had this happen with an L35, which is an industrial tractor with a full "mainframe"
to support the hoe and loader. It is rated to have the outriggers fully support the tractor while digging. So,
even if you dig with the hoe at 90-degrees from the centerline of the tractor, you should not be putting
big sideways stresses on the wheels. How many hours are on this unit?

The OP's L4400 is a light duty "standard" CUT with much less robust subframe and weight. I can see
90-degree digging causing that problem on that tractor, as mentioned above.

Welding a ring of steel to your wheels around the lugs makes sense as a repair, IMO.

SPYDERLK · Jan 26, 2013

CptTrog said:
I tend to agree, Gary. Thanks for the suggestion about thicker/multiple washers. I believe that will likely help the situation tremendously.

Im guessing that your tractor uses the same size studs and bolts as my Ls do. I would use the thick Gr8 SAE 5/8" washers sold by McMaster Carr. Substitute them for the lock washers, and orient them with their rounded surface toward the rim - washers are stronger that way. That washer will put down a 1.25" pressure circle in place of the intense 1.07" circle of the lock washers. That should do it easy if you tighten to full spec. If you feel the need to spread more you could use the std dia and thickness Gr8 under the SAE dia ones. The resultant stepping of stiffness will breed a very healthy situation. Probably overkill, but cheap insurance
larry

CptTrog · Mar 3, 2013

Update on the situation on my L4400. Placed grade 8 flat washers under the lockwashers and have put about 20 hours of work on them. Checked torque after each 3 to 4 hours. Results? Torques have not degraded at all and looks like the lockwashers have better material to "bite" into. Think this is going to work out VERY well.
Thanks for all the great feedback, folks!!