Is it possible for a tractor to have limited slip?

[dcyrilc]

I just did some serious pushing with my tractor last night. Trying to put a tri-axle trailer with 15K# of hay on it back into the barn through the mud. What I found interesting was that when I really got on the throttle, all the tires would spin and throw mud and rock. I've never heard of a tractor having posi/ limited slip, but this is sure how it acted. At low throttle only one rear tire would spin, but when I got on it they would both spin as well as both fronts were spinning too.

My axle lock is non-functional and I was considering digging into it to repair it, but now I'm not sure I want to. This little 50HP 2240 tractor with the duels on it is really a beast. The right side of the trailer never got the axles on top of the dirt, but just cut a path through it. I was pushing dirt/mud with the axles and the frame is only 2" off the ground. The tractor was walking 4 feet sideways back and forth pushing the trailer into the barn. What a ride.:laughing: Not quite the result I was hoping for, but the hay's under cover at least.

Anyway, anyone have thoughts on why I would have power to all 4 (6) tires at the same time?

 

[Reg]

Same happens on cars/trucks that don't have lim slip axles.
If you get enough power to an open axle it will spin both tires, trouble is you aren't getting very much actual BITE - but it looks good (-:

 

[mjncad]

I wish I had a link to a TV news story I saw last week where a Bimmer owner spun his tires fast and long enough on the ice to catch his car on fire.

I'm not sure where the exact ignition point was; but it was an interesting video.

 

[Dmace]

I wish I had a link to a TV news story I saw last week where a Bimmer owner spun his tires fast and long enough on the ice to catch his car on fire.

I'm not sure where the exact ignition point was; but it was an interesting video.

Here's the video on YouTube.

dcyrilc, if your tires were actually getting traction then they would not all of been spinning at the same time unless you had the differential locked. I know I have a foot pedal to manually lock the rear differential but the front is open. I don't know of any tractors with a locking front differential.

 

[k0ua]

Here is the deal, if traction is equal, then all the wheels can spin, you were in a low traction situation, but it is low traction for all axle's so they all recieved equal power. One wheel on each axle can stay motionless or near motionless when it has good traction and the other side has poor traction causing the poor traction wheel to spin at 2X the speed it would normally turn because it is being spun up also by the rotation of the spyder gears which are now turning on their jackshafts as well as the normal rotation of the differential frame. Keep in mind when this situation is happening that the spyder gears are just on bushings and are not made to spin a lot and can get pretty hot. Normally they do not spin at all when traction is equal and you are going in a straight line. When turning they rotate slowly to make up the difference in the wheel track lines, and speed up the outside track wheel. This is what prevents you from "scubbing" when making a turn. I dont know of any CUTS that have any of the limited slip schemes in them. But I could be wrong. When we were kids, (long time ago) we used to abuse our high powered cars on a regular basis. Normally when spinning our tires on the pavement only one tire would leave the beloved J hook black mark. This was usually accomplished by letting the car roll backward down a hill, and then flooring it. But some times only occasionly you would get a perfect 2 J hook marks. This occured when the road conditions allowed a perfect match up in traction conditions on both tires. Then when GM introduced the Posi-Traction limited slip rear axle in 1965 all bets were off. they had a clutch pack arrangement in the rear end, that locked it up and burned both tires. More than one set of spyder gears turned blue, and sometimes locked up on their shafts. :laughing: Not smart, but we did it.
James K0UA

 

[HiTechTed]

When we were kids, (long time ago) we used to abuse our high powered cars on a regular basis. Normally when spinning our tires on the pavement only one tire would leave the beloved J hook black mark. This was usually accomplished by letting the car roll backward down a hill, and then flooring it. But some times only occasionly you would get a perfect 2 J hook marks....
James K0UA

We called that a "dummy drop." We would put the car in reverse, then without stopping throw it in L1 (or whatever gear is on the other side of N) and floor it. It was more fun on country roads where a lot of tar had risen to the surface in patches. Man that was fun, but those poor cars took a beating.

 

[k0ua]

When doing those burn off's with one wheel near motionless, and one tire spinning, usually the speedometer indicated 120 MPH, as the speedo is driven by a gear in the transmission, so the driveline was going 120 and one tire was near motionless, then it follows that the spinning tire is going 240 MPH. It is a wonder that more of those old tires did not come apart.

James K0UA

 

[tcartwri]

when the diff is heavily worn, you can get binding in the sun gears when you apply a lot of power. It effectively locks the diff. That is what you are seeing.

I ran a street car at the dragstrip for a number of years like this. It actually worked better than the posi I eventually replaced it with.

 

[dcyrilc]

Hmmm......

...all interesting thoughts. I would be really suprised if I had perfectly distributed lack of traction. Especially once I got down to the gravel. So far, tcartwri's thoughts make the most sense.

I don't think I have the experiance to recognise worn gears from new gears, but I do have a picture from when I had the 3PH off to rebuild it.

As for the diff lock, I have the pedal also, but it doesn't do anything. The dealer gave me some ideas what to look for to assess what will be needed to repair it. I'll be looking at that this spring after it warms up sime since my shop isn't heated.

 

[gwdixon]

I've never heard of a tractor having posi/ limited slip, but this is sure how it acted.

The Kubota M series from 70 HP up has limited slip on the front axle and a real lock lever. All four tires will spin under the right (or wrong) conditions.

 

[tulenutn2o]

Diff lock is the only thing I'm aware of on tractors, the independent brake pedals work too. As far as autos go, we would set the diffs up with tight clearances and achieve a poor mans posi, short of welding the spiders as in our dirt track cars. Some Ford vehicles have a neat feature in their autos where when it is in 2nd, that is indeed, what gear it is in. This allows reduced power to wheels and tends to control traction better. Sort of like that other power control device................your foot.

 

[Ford tractor]

I wish I had a link to a TV news story I saw last week where a Bimmer owner spun his tires fast and long enough on the ice to catch his car on fire.

I'm not sure where the exact ignition point was; but it was an interesting video.

I'm sure that was a fake video. Not possible to create enough friction to catch a car on fire from an ice burn out.

We called that a "dummy drop." We would put the car in reverse, then without stopping throw it in L1 (or whatever gear is on the other side of N) and floor it. It was more fun on country roads where a lot of tar had risen to the surface in patches. Man that was fun, but those poor cars took a beating.

"Dummy drop" is a good name. I have some splined shafts with all the splines missing from something similar Yes, I used to be much less intelligent!

 

[EE_Bota]

When doing those burn off's with one wheel near motionless, and one tire spinning, usually the speedometer indicated 120 MPH, as the speedo is driven by a gear in the transmission, so the driveline was going 120 and one tire was near motionless, then it follows that the spinning tire is going 240 MPH. It is a wonder that more of those old tires did not come apart.

James K0UA

Does that actually follow? I thought I understood how a diffy works, but now I am not so sure.

 

[Robb71]

Does that actually follow? I thought I understood how a diffy workes, but now I am not so sure.

No, even if only one tire is spinning the speed of the tire does not double.
The speed of the tire (one or both) is limited by the engine rpm and gear ratio. Theoretical top speed of the car is the same as the max speed the one tire will spin. Actual top speed of course is less due to friction, air resistance, etc.

 

[tulenutn2o]

No, even if only one tire is spinning the speed of the tire does not double.
The speed of the tire (one or both) is limited by the engine rpm and gear ratio. Theoretical top speed of the car is the same as the max speed the one tire will spin. Actual top speed of course is less due to friction, air resistance, etc.

Plantetary action comes into play.Check out this link for an explanation.YouTube - How spider gears work.

 

[EE_Bota]

No, even if only one tire is spinning the speed of the tire does not double.
The speed of the tire (one or both) is limited by the engine rpm and gear ratio. Theoretical top speed of the car is the same as the max speed the one tire will spin. Actual top speed of course is less due to friction, air resistance, etc.

Thanks. I could have tried to prove it to myself, but unfortutely, my Subaru Baja has limited slip, and a viscous coupling between front and back, and it will take any attempts at playing as a challenge to destroy the garage.

I asked some folks in the shop, and they said the free wheel will double. Then they said, they didn't know if it would double, but it will go right much faster.

 

[EE_Bota]

Plantetary action comes into play.Check out this link for an explanation.YouTube - How spider gears work.

Thanks! Most times when I know my tire is slipping, I have never been in a situation to SEE what that means. And even when on the tractor, I find I can't actually look (too risky) and even when I glance, it looks like a brown mud covered blur.
It is nice to learn something new, only for the price of asking!

This was also very good.
http://www.youtube.com/watch?v=K4JhruinbWc&feature=related

 

[tulenutn2o]

Thanks! Most times when I know my tire is slipping, I have never been in a situation to SEE what that means. And even when on the tractor, I find I can't actually look (too risky) and even when I glance, it looks like a brown mud covered blur.
It is nice to learn something new, only for the price of asking!

This was also very good.
YouTube - How Differential Gear works (BEST Tutorial)

I posted that link because I couldn't find the words to explain it, I must suffer from ALLTIMERS! I'm glad it helped. I saw that other one too, but the 4WD one was crystal clear-with no way to argue against.

 

[tcartwri]

I'll put my vote on post #5. The mention of planetary action and sun gears was made. Neither are in the common automotive axle.

You might want to look into that a little bit more.

 

[RickB]

You might want to look into that a little bit more.

K7LN is correct. Don't confuse a planetary unit with a differential. You might want to look into that a little more.

Some tractors have locking front and rear differentials. Some MFD tractors have limited slip front axles. I know of no tractors with limited slip rear axles, but am willing to be educated.