Traction My Tractor Slips Going Down Hill While Mowing

[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.