In this post we are going to take a look at a very common service complaint that affects a wide variety of early Kubota B and L series tractors – steering box failure! In a follow up article, we will examine how to undertake a steering box repair and overhaul.
Symptoms of Steering Box Failure
The number one symptom of a failed steering box is that the steering will feel real loose and the front wheels of the tractor may wobble and oscillate. This is because the internals of the steering box are no longer integral and tight. Symptoms of steering box failure include:
- wobbly steering
- mushy, loose or unresponsive steering
- raising the front of the tractor with a jack – grinding or resistance when turning wheels from lock-to-lock
- shaking the steering wheel – feels really loose and ready to come right out of the tractor
If your Kubota B or L series tractor exhibits this type of wonky steering, do not ignore this repair! It is foolish and unsafe to operate your Kubota this way.
What Causes this Failure?
Typically, steering box failure is caused by 3 conditions, all working together to break your Kubota:
- Upper Steering Column Bushing Wears Out
The failure of the steering box is most likely due to water making its way into the steering box through a defective, missing or worn bushing at the top of the steering column.
This thick rubber bushing holds the steering shaft centered in the steering tube. When new, this bushing fits very tightly against both the steering shaft and the inside of the column tube. After several years of steering and turning your Kubota tractor, this bushing wears out and is no longer tightly holds the steering shaft.
Tractor is stored outside in the elements allowing rainwater to trickle down steering shaft. A few drips at a time, this rainwater will run down the steering shaft and toward the steering box.
- A Plugged Weep Hole
Kubota did engineer a back-up fail safe into the steering box and column to prevent catastrophic failure and keep water our of it – a weep hole. Unfortunately, very few owners know of this back up weep hole system and as such do not service it.
At the very bottom of the steering column, where the metal tube mates to the cast iron housing of the steering box, there is a small weep hole facing downwards. If you look closely at this picture you can see that the weep hole appears solid and plugged.
The next step in the chain of events that leads to a broken steering box is that over a period of time, rainwater, dirt and debris make their way down the steering shaft and eventually plug the weep hole.
Weep Hole? A Big Deal?
You bet! The weep hole is located just above the lower steering column seal and bearing. This seal is a typical rubber friction seal that is spring tensioned. When the weep hole plugs, the entire steering column can fill with a head of water, dirt and junk. Since this moisture can no longer egress the column, the water will begin to move past the seal, right into the steering box – this is bad.
Since oil floats on water, the lower bearing that supports the steering shaft begins to go unlubricated causing severe wear. Once infiltrated with moisture and water, the bearings fail falling apart causing the steering shaft to wobble.
If the excessive wear on the steering shaft was not enough to destroy the steering box, then the first time the temperature goes below zero, the water in steering box freezes, causing expansion that fractures the box case – either out the bottom or it cracks the case on the sector shaft side.
It’s unfortunate when steering box failure occurs like this since that little hole can be easily cleaned out with a small drill bit rotated by hand.
I am also of the opinion that steering box failure is somewhat of a service secret at Kubota. You will not find a shred of info in any Kubota service literature, technical service bulletin or technical training manual that discusses keeping that drain hole clear, yet Kubota sells replacement steering box shafts and bearings by the truckload!
Some tips to prevent this type of failure from occuring with your Kubota:
- locate your Kubota’s steering system weep hole and get in the habit of clearing out the dirt and debris – a simple drill bit rotated by hand is enough
- avoid parking your Kubota out in the rain which allows water to travel down the steering shaft toward the box
- inspect and replace the upper steering column bushing if its worn out or oblong
Too Late. I’ve got a ruined Steering Box.
Okay, not to worry. If it looks like the steering box on your Kubota tractor requires an overhaul, or the box itself has a pressure crack due to freezing – stay tuned. In the next installment we will take a look at how to undertake a steering box repair job!
Service Department Vic