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Why ball differentials?

Why ball differentials?

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Old 01-27-2011, 09:39 AM
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Default Why ball differentials?

So I realize that ball diffs are not included in some RTR stuff because they are relatively easy to mess up...but what I cannot figure out is why most "factory" cars have ball diffs instead of gear diffs. It seems to me that there should be no difference between the two if you use the correct oil viscosity. In fact, the gear diff should be more tunable because one can use a huge variety of oils. I am contemplating switching out my SC10 ball diff for the gear unit just to see what it feels like.

What are the pros and cons of ball and gear differentials and why are gear diffs relatively rare in race circles?
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Old 01-27-2011, 09:55 AM
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In theory you should be able to get a gear diff to handle the same as a ball diff. But consider that you have to tear apart the tranny, pull out the diff, take it apart, clean all the pieces, reassemble with a different oil or grease then put back in car just cause the track changed since you started running or you showed up at the track with the wrong setup.

One the SC10 a ball diff you just pop a ball joint, pull the bone out, turn a screw and you're done.

Ball diffs, while they require more maintenance, offer much easier tuning on the fly.
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Old 01-27-2011, 09:55 AM
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Gear diffs are great for a low-no maintenance item.

I find myself either relubing, rebuilding, or flipping rings about every 8 races or so. But the nice thing about the ball diff is that i can adjust it on the fly without breaking down the whole rear and tranny...

I can tell a huge difference between the two on my indoor clay track im currently running on. Ive tried all sorts of oils in the gear diff from 25 wt shock oil to 500 and 1k diff oil. Of all of those i prefer 40 wt losi.

Still though i prefer the ball diff, i tinker with my stuff often enough anyway. I love to be able to adjust it in 10 sec on race day. Not only that but it feels like it holds a corner better than the gear diff and doesnt break that inside rear wheel loose nearly as much as the gear diff when punching out of a turn nor doest it make the rear end dance down the straight under power like the gear diff did.

For racing ball diff gets my vote but i will chose a gear diff in anything i decide to bash.
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Old 01-27-2011, 10:10 AM
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The feedback I got from some of the Pro level drivers I have talked to is that the gear diff can be tuned to be better for a certain part of the track maybe, but they never had any luck getting it to work as consistently all around the track.
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Old 01-27-2011, 11:15 AM
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Gear diffs are great for a low-no maintenance item.

I find myself either relubing, rebuilding, or flipping rings about every 8 races or so. But the nice thing about the ball diff is that i can adjust it on the fly without breaking down the whole rear and tranny...

I can tell a huge difference between the two on my indoor clay track im currently running on. Ive tried all sorts of oils in the gear diff from 25 wt shock oil to 500 and 1k diff oil. Of all of those i prefer 40 wt losi.

Still though i prefer the ball diff, i tinker with my stuff often enough anyway. I love to be able to adjust it in 10 sec on race day. Not only that but it feels like it holds a corner better than the gear diff and doesnt break that inside rear wheel loose nearly as much as the gear diff when punching out of a turn nor doest it make the rear end dance down the straight under power like the gear diff did.

For racing ball diff gets my vote but i will chose a gear diff in anything i decide to bash.
+1 good explanation.
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Old 01-27-2011, 11:18 AM
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As I understand it’s because of the way a ball diff responds differently to load.

Under no to low loads, rolling through a corner, a ball diff is fairly free, allows for good turning. But then on power/acceleration the ball diff binds up some, acting as a limited slip, preventing one wheel from spinning loose.

A gear diff needs thick fluid to prevent spinning one wheel, or “diffing out” as some call it, under hard acceleration loads. But that thick fluid doesn’t allow for good turn in going through the corner. Always a compromise.

Believe ball diffs are generally lighter with less rotating inertia as well.
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Old 01-27-2011, 11:48 AM
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+1 on previous posts. Gear diffs generally are easier to drive due to many of these explained characteristics.
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Old 01-27-2011, 09:27 PM
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Thanks for the info, fellas!
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