Traction My Tractor Slips Going Down Hill While Mowing

[RickB]

And while we're on the topic, check the rear tire pressure. Could be another situation where the tires are spinning on the rim.

I’m more of a mind that his turfs are overinflated if anything. Post #11.

 

[Egon]

How about the pedal adjustment for neutral ?

 

[k0ua]

If he had all the answers he would not need to ask the question. Clearly he is less than happy with the responses. That happens.

If someone can explain how a hydrostatic transmission can freewheel in 2wd but not in 4wd on the same slope and conditions I am willing to learn.

Please add me to that list of eager learners.

 

[ruffdog]

Hey, it is cold and rainy here....what else am I to do? Just throwing out some ideas for the OP. It's all good! :drink:

 

[k0ua]

+1. And this is why I disagree if the OP thinks it's an internal issue. Internal issues would exist in 2WD or 4WD and affect both equally. If it goes away in 4WD then it's a traction issue and not an internal issue. These "4WD" tractors are really like having an extra FWD assist driven off the RWD. If the front driveline is not slipping internally then that means the rear is not slipping internally.

Yep, it is simple logic.

I have seen many cases where people ask for help, and then discount that help because they did not believe it was valid. And that is fine by me, but I still know it is rear tire slippage because of weight transfer because the front wheels are going downhill and now carry more weight and the rear tires which are uphill now do not carry as much weight. A simple vector sum problem. Oh well. It is absolutely silly and potentially dangerous to go down any steep hill in 2wd, that is just asking for trouble, and the OP proved to HIMSELF that putting the tractor in 4wd solves the problem. The OP described problem is a very common one that has occurred to almost all of us that live in hilly country. It has happened to me when I forget to have it in 4wd going down a couple of my steep hills. Think of the tiny contact patch of the rear wheels, think of the loss of weight on the rears from going downhill nose first. To the OP, leave it in 2wd and go down the same exact place as before in the exact same conditions it slipped before only now go down in reverse with your rear wheels downhill, and it won't slip because the weight transfer is now helping you instead of hurting you.

 

[dadiehl]

I had a JD 3320 hydrostatic tractor. Going down any steep slope it always was a toboggan ride if I had it out of 4 wheel drive. Every so often I would forget and down we went.

 

[Industrial Toys]

I have never had a slippage (loss of adhesion) incident where there wasn't quite clear evidence of that on the terrain.

 

[bill18163]

Thanks guys for all the input. I can guarantee you that the tires are inflated correctly. I am a very precise person by nature and I even get mad at myself if I make a stupid mistake. Just recently as the weather cools I reminded myself to check tire pressure on both our cars since cooler weather will lower the tire pressure. Yep, I had to add air to both car's tires. One thing I am going to do is try to pay close attention to how this happens. I am going to try to get it to do it while I am watching closely to see if I can pick up the cause. I'll try it on not too steep a hill to be safe. I also will check that transmission fluid just to be sure.

 

[RickB]

I have never had a slippage (loss of adhesion) incident where there wasn't quite clear evidence of that on the terrain.

So what is happening to the OPs tractor? Got any constructive input?

 

[SDT]

I have a B2710 with hydrostatic trans with 800+ hours on it. If I go down a hill on my property while mowing, the tractor will slip internally and get going too fast. It will not hold back and go down the hill slowly under control. It will "take off" so to speak. Now if I run the tractor in four wheel drive it will not do that. It only does it in two wheel drive. I have two other Kubota tractors and they will not do this sort of thing. In either two or four wheel drive they will creep down a hill under full control. This happens while coasting with my foot off the accelerator just using the weight of the tractor to coast down the hill. It will break loose and not hold back like my other tractors. Anybody have any ideas what could cause this?

It's not slipping internally. One or both rear tires is/are slipping.

This is why things are as they should be when in FWD.

SDT

 

[Industrial Toys]

I think it's EXTREMELY constructive. Sometimes making observations is more valuable than coming to conclusions and blurting out possible causes. Often (here) like it's a contest with free entry. More than before, I think the OP is quite competant. And YES, I could be wrong.

I will be the first to admit that I dont' always read the OP slowly enough and give it enough thought. Easier to ask, is it plugged in.

 

[crazyal]

I would try the diff lock test as mentioned in an earlier post. With an open diff only one wheel needs to break free. I think most people are pointing you that direction simply because it's the most likely case. It's also the cheapest problem. In my mind the only way I could see 4wd acting differently if it was an internal problem is if you were turning while going down the hill. That would cause a little binding but the traction would need to be very good. Obviously in 4wd turning on pavement it shows up but on grass, I wouldn't think so.

 

[k0ua]

Thanks guys for all the input. I can guarantee you that the tires are inflated correctly. I am a very precise person by nature and I even get mad at myself if I make a stupid mistake. Just recently as the weather cools I reminded myself to check tire pressure on both our cars since cooler weather will lower the tire pressure. Yep, I had to add air to both car's tires. One thing I am going to do is try to pay close attention to how this happens. I am going to try to get it to do it while I am watching closely to see if I can pick up the cause. I'll try it on not too steep a hill to be safe. I also will check that transmission fluid just to be sure.

Better yet, enlist the aid of another observer standing to the side to observe the rear wheels. You will see that the wheels/tires do not keep pace with the speed of the tractor. In fact one tire can even rotate slightly backwards due to the differential action. It is a rather interesting phenomenon. To help get this loss of traction between the contact patch of the rear tires and the ground, put more weight in the front end loader. This will help "unload" the rear tires even more by utilizing the pivot point of the front axle as the fulcrum.

 

[ruffdog]

Better yet, enlist the aid of another observer standing to the side to observe the rear wheels. You will see that the wheels/tires do not keep pace with the speed of the tractor. In fact one tire can even rotate slightly backwards due to the differential action. It is a rather interesting phenomenon. To help get this loss of traction between the contact patch of the rear tires and the ground, put more weight in the front end loader. This will help "unload" the rear tires even more by utilizing the pivot point of the front axle as the fulcrum.

With a open differential, if one wheel stops, the other will travel twice as fast. If one wheel only slows to half speed when it slips, the other one will travel 50% faster. When you are going down a hill with a tractor, 50% faster has a high panic rating.

 

[crashz]

Just to play devils advocate here, and this probably points even more towards the groups position:

Could a stripped tooth on a final drive pinion do this under just the right conditions? The hydro pedal is returned to center and one pinion gear is left in a position where a broken tooth or teeth should be in contact with the bull gear. This would allow free wheeling of that side and consequently free wheeling of both side. But - you'd know if you had a broken final drive. It would be all out of sorts under all conditions.


I've "free-wheeled" down hill in the same conditions that the other posters have mentioned. And it does feel like internal slipping. Because when it happened to me, I spotted one rear wheel not slipping in the grass, but rolling quickly downhill. Which does cause slight gear whine as the other wheel is frantically spinning uphill with no purchase.

 

[Diggin It]

I don't know about y'all, but when I commence to speeding downhill more or less uncontrolled, I'm looking forward trying not to hit stuff. I'm not looking down at either rear wheel. When I get stopped, I look back for skid marks ... not just on the grass.


I've done it a few times and I'm learning to remember not to do it again. USUALLY, I see one track torn into or through the turf, but there have been a couple of time when no such track was noticeable. I told the tale here some time back about rolling downhill backwards where one tire was slipping on the rim due to the leaking beet stuff.

Is the OP slipping over the grass?
Is a tire slipping on the rim?
Or does he have some legitimate internal transmission issue?

Possibly only a test with observers on both sides of him closely watching all four wheels and tires will tell him for sure what's happening.

What puzzles me is why the smaller 18XX doesn't slip. Then again, we don't know the degree of slope involved or how all three tractors are configured.

 

[JethroB]

The OP issue reminded me of a Paul Short video regarding a Kubota BX model that had a very long rollout and would coast after your foot is removed from the HST pedal. The transmission was slow to give the quick braking affect most people expect. Sort of like engine braking we expect when decelerating. I have a Chevrolet SUV automatic like that, sucker will speed up going downhill when on cruise. Its going to get me speeding ticket one day.

Two Concerning Questions on the Kubota BX25D - YouTube

 

[k0ua]

Just because tractor A slips going down hill in 2wd and tractor B does not, proves nothing other than tractor A is not tractor B

Tractor B may have a different set of tires and a different weight distribution.

When one hears the sounds of hoofbeats on the ground, one should normally think horses instead of zebras. Unless one is in Africa of course.

By the way, there have been members here in the past that have taken the "wild ride" and did not fare so well. Some have crashed into trees and some have even overturned their tractors trying to avoid said same. Usually it just requires a change of underwear, but it can be serious.

 

[Industrial Toys]

Yeah. If your gonna subject yourself to that possibility, make sure you at least have the room to go somewhere and not into something.

 

[RickB]

Thanks guys for all the input. I can guarantee you that the tires are inflated correctly. I am a very precise person by nature and I even get mad at myself if I make a stupid mistake. Just recently as the weather cools I reminded myself to check tire pressure on both our cars since cooler weather will lower the tire pressure. Yep, I had to add air to both car's tires. One thing I am going to do is try to pay close attention to how this happens. I am going to try to get it to do it while I am watching closely to see if I can pick up the cause. I'll try it on not too steep a hill to be safe. I also will check that transmission fluid just to be sure.

I would be interested in hearing how much pressure you are running in those rear tires.