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Discussion Starter #1
I have a 1974 super convertible that I recently picked up. When I brush hog I notice that only the left wheel turns to drive the tractor. Should both wheels turn for 2 wheel drive or only the one?
Thanks, Mike
 

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Welcome!

There's a differential in there, with no limited-slip or anything, so if something stops one wheel, the other turns twice as fast.
If you jack up the machine, both wheels off the ground, can you easily turn them both? When you turn one does the other go the opposite direction? If so, you're fine. If one wheel is jammed, that points to some spectacularly messed up wheel bearings. Not a hard fix, but you'll have to take the axle housing off to get in there.
 

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Discussion Starter #3
Thanks for the reply. But when you use the machine does one wheel drive it with slip differential or is it 2 wheel drive all the time? Thanks, Mike
 

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I'm not really understanding your question.

It's just like a non-limited-slip car differential. (Literally the same gear arrangement as some older cars)

When you're running, there's force being exerted by both wheels. If one wheel starts to slip badly, it will just spin. There will still be some force exerted by the other wheel, but not much, only the residual force from the slipping wheel. Those statements are true regardless of which wheel slips.

A limited-slip differential attempts to compensate for that by reducing the force applied to the spinning wheel and increasing the force to the other wheel. There were some gravely riders with LSDs, but none of the walkers ever had them. There were steering brakes, which allow you to brake one wheel or the other, those can help if you find yourself spinning a wheel.
 

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The way the differential works is, it splits torque 50/50. Of course, if it only takes 2 ft/lbs to roll one tire over, that's all the other side gets as well...... Doesn't matter how much power the engine is putting out.....
 

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Discussion Starter #6
HeyYou and JRD, thanks for the reply. I'm having a brain freeze about this so let me explain why I asked the question. The tractor runs great and as we know it is powerful. However I noticed that when I get "stuck" like in mud or loose soil on a hill only the left wheel is turning, The right side does not turn. Shouldn't both wheels be spinning and driving the tractor? Seems the right wheel should also spin to provide power to the drive train. I Also wonder if I have the gear shifters set right. It is the 8 speed and I had both levers in the low position. Thanks
 

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When the left wheel starts spinning wiggle the handle bars left and right a little. That will shift power threw the axles making the left and right tires turn a little at a time. Other wise your stuck. Changing the tires to a different thread pattern maybe the way to go..
 

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See the exploded diagram of a differential at Exploded view of a differential by René-M. Viette, 1945, or google others. This one is for a car, but the core part of it is identical to a gravely.

The parts which matter are the two "planetary" gears, and the "satellite" gears on the shaft in the middle. The ring gear turns the housing in which the shaft of the satellite gears is mounted. IOW, the ring gear is not directly tied to either of the axles. It turns the satellite part in the middle, and that in turn drives the axles.

In normal operation, going straight ahead, the satellite gears are not turning. They stay motionless on their shaft, while the entire assembly is rotating, driving the axles.

Now think about what happens when one axle gets stopped. The only way for the satellite gear shaft to keep rotating is for the satellite gears to turn against the stopped axle. That means they're turning the other axle twice as fast.

Now think about what happens when one axle starts to spin. It's exactly the same thing. That axle turns faster, allowing the other one to stop.

When you're running the tractor around and turning, the same effect happens to a lesser degree. The wheel on the outside of the turn has to go a longer distance than the wheel on the inside of the turn. Therefore it turns faster, and the inside axle turns slower. The satellite gears rotate to compensate for the differential axle speeds required by the turn. Thus the name :)

If when you spin a wheel it's always the left side, I chalk it up to coincidence. Try putting the right wheel in some mud and butt the nose against something immovable. You'll get exactly the same wheel spin on the right.
 

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My understanding is that gravely was asked why a limited slip clutch wasn't offered, and reportedly the answer was that it wouldn't fit. Or so its claimed by some. The next best idea maybe is finding a replacement parts set that makes it a "solid" axle I had a parts list for that once maybe somebody else knows.
 

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My understanding is that gravely was asked why a limited slip clutch wasn't offered, and reportedly the answer was that it wouldn't fit. Or so its claimed by some. The next best idea maybe is finding a replacement parts set that makes it a "solid" axle I had a parts list for that once maybe somebody else knows.
Huh. I find that hard to believe. The 800 series were available with an LSD. That unit fits in the same form factor as the regular diff. And it's about the same size as the walker diff.

I bet the reason was more about saving money :)

Re solid axle, I can't see how it would work to have an actual solid axle. You'd never be able to get it through the splines in the diff. But I bet you could find a way to stop the center pinion gears from turning. That would stop the differential action, essentially giving you the effect of a solid axle.

But I question how usable such a machine would be. The gravely isn't insanely heavy, but it's heavy enough that it would be a bear to turn on solid ground.
 

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My thought exactly. It a bugger to turn in tight quarters now. I would think steering brakes would be a better option. Just using the brake to load the spinning wheel.
Not sure what you are using for tires but I am having thoughts about changing the turf tires to something else.
 

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I would think steering brakes would be a better option. Just using the brake to load the spinning wheel.
+1

Not available on L models, though :(

Another thing that helps is duals.
 

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You mean the flanges with the four bolt holes? Mounts for GRWs.
 

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Once you have mounted GRW like maybe on a L ground speed L for dirt plowing its very tempting to get another tractor for other needs rather than continually swapping things around.
 

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Even the little I have looked for GWR's. Looking for a machine already equipped would be the way to go. Yes the lower gear would be nice but just not worth the cost on a LI.
 
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