Tractor rear end question

[Anonymous Poster]

Hi,

When putting chains on the rear of my B2910HST today I noticed something that I did not expect. I could spin one wheel and the other did not move at all.

Forgot to mention that I had a floor jack lifting both wheels off the ground.

The transmission was in neutral, the brakes off and 2wd selected.

I was expecting that when one wheel was turned one way, the other would go the other way...like in a car.

Seems like the rear wheels are independent...does this have something to do with having a hydrostatic transmission?

Puzzled here...don't have a clue!

Bill in Pgh, PA

[Anonymous Poster]

Others can correct me in i'm wrong [img]/w3tcompact/icons/grin.gif[/img]
I have HST also, i think this is normal.

I noticed once when I had 2wd on (forgot to hit 4wd), and was going downhill slowly with my FEL attached, no ballast, slight grade to level ground, I started to go faster... The grass was wet and the left rear lost traction started to spin backwards and the right rear just kept going forwards. I hit the level spot,
left a left rear skid mark about 3 feet, no biggee....

I know my riding mower, hst... if i lose traction, one tire like you said spins, while the other spins just the opposite. Not much fun

[GaryM]

In an auto with a manual transmission in neutral, and both wheels off the ground and you spin one, the other might not spin at all. The drive shaft might spin instead! Depends on where the friction is. With an automatic transmission in PARK, the drive shaft is locked and the energy goes to the other wheel. I'd guess that with the HST transmission the energy would go into the HST as there might be less friction there than in spinning the other wheel.

It's been a few years back since I've done this. I don't remember what happens with a limited slip differental.

[RobS]

Bill, your tractor has a differential in the axle just like a car. It allows the wheels to spin at different speeds as you turn a corner. What you observed was the input shaft turning instead of the other wheel but since the input shaft is buried within the tractor you couldn't see it.

I don't know that much about HST, but I believe the rear end would be the same. Only the power source to the rear end may differ. The PowerTrac guys (and a few others) have a totally different set up with independant hydraulic motors at each wheel.

Hope this helps [img]/w3tcompact/icons/smile.gif[/img]

[MossRoad]

Yeah, no differentials at all. No transmission. But no neutral either. If the engine stops, you ain't going nowhere, never. If you need to tow it you have to do something to the hydraulic pump; install a bypass hose, I believe, which lets you tow it. Not too hard, from what I hear. There are downsides to every design. [img]/w3tcompact/icons/smile.gif[/img]

[Anonymous Poster]

HI,

I agree it must have been the input shaft spinning...

I guess I could prove it by putting the tractor in 4wd and then trying to spin one of the wheels both were in the air.

Thanks for the help. Sometimes the obvious is not so obvious!

Bill

[RobertN]

Your wheels will turn independantly. That's the "differential" effect. You car or truck is the same way.

When you turn, one wheel moves at a faster(outside wheel on the turn).

Now, if you do have both wheels turning, it is harder to turn. That is why the book says not to use the Diff lock if you need to turn(at least my book does). Both wheels will turn at the same speed, wanting to push the tractor forward. Try it on a soft surface some time.

You'll note some 4x4's and hot rods with limited slips, and especially true posi's or "lockers" will chirp thier tires when turning into parking spaces or making other tight turns. This is because the posi precents the outside wheel from truning at a different speed than the inside.

You'll note that most "2 wheel drive" vehicles are really only one wheel drive. For a 4x4, they are usually only really 2wd, one rear wheel, and one front wheel. This of course, changes when posis and lockers are added.