Traction Kubota BX 2370 out of control on hill in 2W drive

[RaydaKub]

Brakes on a hydro tractor are almost worthless except to park. The hydro is designed to go forward and backward. In between the two is, in theory, no motion of the wheels. Doesn't matter which way the wheels are stopped, hydro or brakes, they are stopped. If the wheels are stopped and the tractor isn't, well, then you're skidding.
K0ua mentions the effect of one wheel freewheeling forwards and the other spinning backwards and that certainly does happen, but once you get started and lose traction, the odds of having the other wheel stop you before you level off are pretty slim in my opinion. Like he said, it's the gift that keeps on giving.

 

[k0ua]

So does this mean the "brake" is actually not on the axle but rather on the "drive shaft" with the differential between the brake and the wheel? Boy, I can't wait to look at my service manual tonight to be sure. I assumed the brake was on the axle. Always learning at TBN!!!

The brakes are one on each rear axle. and I am sure when he stomped the brakes to the floor both rear wheels/tires stopped all rotational motion.. But that ain't gonna stop a tractor skidding down the hill. Not until the ground flattens out some. When I mentioned the differential action and the possibility of one tire going forward and one backward that is without the brakes applied. Jack up your tractor in the center so both wheels are off the ground and place transmission in Neutral, and rotate one wheel/tire forward and the other will go backward.

What causes the slide to start in the first place is the engine RPM and the output of the transmission is going slower than gravity wants to pull the tractor down the hill. Also with the down angle of the tractor, the majority of the weight of the tractor is on the front axle. Now the rear tires are "light" The engine/transmission is starting to act like a brake, attempting to slow down the forward motion of the tractor. Eventually the tires contact patch breaks traction with the surface of the ground.. Whoops, once broken, it is very hard to regain, as the forward velocity of the tractor is increasing faster and faster and the engine/transmission "brake" is still attempting to slow down the wheels and tires.

You are out of control in a slide.. NOT freewheeling. The tires are not turning fast enough compared to the velocity of the tractor. If you floored the hydro pedal to increase speed of the wheels/tires you might get it to "catch", but it is doubtful. Standing on and locking the rear wheels by braking doesn't help, the contact patch of the tires have no traction to begin with and braking sure isn't going to improve that any. You are on a one way ticket express train to ......Whee, Haww.. hang on..!

 

[jeff9366]

Going down hill tractor weight shifts forward, so the rear wheels "unload" and may not grip even if locked up.

 

[TripleR]

It's normal as others have said, happened to MissouriThunder several years ago and about scared him to death. I came close on my L5030, but like James recommended, I pressed on the go pedal to regain control and steer.

 

[RaydaKub]

Yeah, freewheeling was not an appropriate term.

I've mowed my hillside for a number of years in the fall for the kids to go sledding in the winter. My little STX38 would slide down a lot. First time was a major thrill. After a few trips down I figured out that all I needed to do was steer through it and hang on. The last couple years it was kind of fun. But I always use 4wd with the BX.

 

[dragoneggs]

I learnt real quick on my hills, soiled myself, and now I keep by BX in 4WD all of the time. I would love to have an audible indication that it is in 2WD.

 

[k0ua]

I learnt real quick on my hills, soiled myself, and now I keep by BX in 4WD all of the time. I would love to have an audible indication that it is in 2WD.

With your hills and terraces, you probably don't have any use for 2WD at all do you?

 

[dragoneggs]

With your hills and terraces, you probably don't have any use for 2WD at all do you?

Me? Nope... I have a big flat driveway parking pad in front of my garage that sometimes I putz around on and don't like the feel of the 4WD so I sometimes shift out but I keep telling myself I'm going to forget again and it's gonna bite me.... :shocked:

 

[rjkobbeman]

On the BX the "brake" is a brake on the differential ring gear. (On the BX the ring gear (as in ring and pinion) is actually not bolted around the differential carrier, however that is not very relevant here.) The foot brake stops the differential. In 2wd, if the differential lock is not engaged, if one wheel is off of the ground the wheels will spin freely... even if the brake is on. In 4wd (and the diff lock is not engaged) if one rear and one front wheel are off the ground (or not very good traction), the same "free wheeling" can take place.

If you remember the brake is stopping the differential ring gear (and by connection, the differential carrier), this all makes sense. There is no braking of the individual wheels or axles. This is why guys report no brakes when they blow out their differential (end and/or spider gears)... usually from a busted diff lock.

Now, my M8540, the brakes actually brake each left and right axle.

In all cases, you must be in 4wd to get "braking" with the front driveline.

If going down (or up) a questionable slope, use 4wd AND lock the differential.

A side note, which I am trying to verify... I 'm pretty sure the "brake" does not disengage the HST/pedal (force the pedal back to neutral). So if your pedal is slow to return to neutral (which mine is -- going to work on that when I have time), if you hit the brake you are fighting against the hst. Also, the "brake" is mean to be a parking brake and not an actual brake to slow the tractor. Its brake discs (an alternating "pack" of steel, pad, steel, pad discs like a dirt bike clutch pack) are minimal and can be worn out / burnt out fairly easily. I'm going to get my hst/pedal adjusted better so I am less likely to hit the brake.

 

[meos1]

I learnt real quick on my hills, soiled myself, and now I keep by BX in 4WD all of the time. I would love to have an audible indication that it is in 2WD.

Use that same swtch sensor Paul SHort used for the back up claxon as the sensor when the 2wd is engaged. Might want to put a defeat on so it does not draw gun fire when you have it off.