Ball Diff? Gear Diff? What's The Diff?

[Saito 5]

What actual benefits does a ball diff give over a gear diff? I understand that a ball diff gives a racer control over the amount of differential action taking place. Other than that, what else does it do? I raced off road very mildly back in the late 80's and everybody was ball diff crazy. Many racers I knew actually ran them too loose to control wheelspin. This was the era before slipper clutches becoame the norm. I know that's not the "proper" use of a ball diff. Some have said their action is smoother than that of a gear diff, but I fail to see it. Full size autos use a gear diff. Is a ball diff like a limited slip device in a real car? The only reason I ask is that I notice many folk turn their nose up at a gear diff. Gear diffs don't wear out like ball diffs do however.

[twisty 8]

A ball diff still allows drive to both wheels unlike a gear diff where drive is lost to the spinning wheel untill the car slows and traction is regained.

A ball diff still gives drive(faster exit from a corner),but can also cause the whole car to slide,so needs a more sensative driver to control the slide,ie, it is easyer to spin out with a ball diff,gear diffs are better for novices or if you have trouble with restraint of the throttle.

[94eg! 834]

It's not about them being smoother. The ball-diff's advantage is that it can keep power going to the wheel with grip. With an open (gear) diff, when one tire looses traction during a turn, the gears automatically transfer ALL power to the wheel with least resistance (grip). This means you completely loose all ability to maintain or increase speed.

By increasing the stiffness of the differential action, you can reduce the difference in power application to either wheel. As much torque as it takes to spin your differential by hand, is how much torque will continue to power the wheel with grip. A tighter diff puts more power to the griping wheel, but too much will make the car hard to drive.

I like to add super thick Anti-Wear grease to my gear diffs. This makes them difficult to turn, and keeps the power going to the wheels in a turn. The only problem is that this effect is not adjustable, and wears off over time as the grease wears out or moves off the gear teeth. This mod made a WORLD of difference in my Hotshot. I could actually accelerate when turning afterwards...

[Rogueraven 0]

Diffs deliever the torgue to the wheels without them the car would be very nasty at handling anyway

Gear Diffs. when cornering the outside wheels ultimately runs faster then the inner wheels. the diffs allow for slip on the inner wheels during cornering slowing them so the car turns better. you lose traction on the inner wheels using the geared diffs because there less precise. thou gear diffs wear less but can increase tire wear.

Ball Diffs allow for a smoother torgue adjustments. giving more traction to the inner wheels during cornering as a result you get improved handling. improved tire wear however Balls diffs are more prone to wear because they worked harder then gear diffs. less forgiving also during corner the traction gained on the 2 wheels can easily become traction lose on all 4 wheels the harder you push during corner

this is my understanding of how they work and i think from what you put you already might have known this anyway sure someone else might correct me or we got anything wrong. anyway in RC Terms i think the ball diffs are the better option

[PSXBatou 2]

I will most likely be replacing both my front and rear diffs with ball differentials. Of course after just spending around $220 in TT-01 Tamiya upgrades I think this will not be until next month at the earliest.

If you use the AW Grease on your bevel gear diff it makes a big differnce, I laid it on thick on my front diff and all the gears around the front drive and I loved the returns on doing that.

[Saito 5]

Thanks, I think that cleared it up for me. I have one more ball diff question. What does a ball diff do when used in a central location like the Avante series of cars? I know they offered a torque splitter option to replace it. Its my understanding that a torque splitter allows the car to be basically 2wd until 4wd is needed. Does a central ball diff here just balance power back and forth between front and rear wheels?

[Wrc action 0]

Ball diffs are RC's equivalent of limited slip diffs in cars.

there are however a few problems that being that they can eat themselves if over tightened and have a habit of coming undone at the most inconvient times. They need more maintenance than a normal gear diffs.

there is also 2 ways to get a ball diff style effect from a gear diff. one is the AW grease as mentioned however this can leak out and as the diff works the greases temperature will change and as thus its effect often losening back to a normal diff by the end of a run/race.

The second way is to add shims into the sides of the diff. therefore pushing the cogs onto each other slowing down there action. it takes time to get it set up just right but once done is very reliable and needs no checking/maintenance unlike the normal ball diff.

Hope this helps

Ryck

[twisty 8]

A torque splitter,is like a one way bearing(always fitted to the front drive),it allows front wheel drive in the forward direction but not in reverse,so basicly the stearing is a bit more responsive,there is slightly less friction in the drivetrain so gives a little more speed.

There are two more important effects of fitting a splitter

1:the brakes will only work on the driven rear wheels (good for a drifter=handbrake effect)very hard to control braking

2:there is no drive from the front wheels in reverse.

[94eg! 834]

During a turn, the front wheels follow a larger radius, and therefore need to spin faster than the rears to keep in contact with the road.

For a regular 4WD with no center diff or torque splitter, the front tires will typically loose traction during a turn because they are forced to travel at the same rotational speed as the rear. This causes under-steer.

A center ball-diff (like Avante) allows the front wheels to maintain proper rotation during a turn. In addition, the limited slip effect of the center diff keeps the drivetrain from transfering %100 of the torque to tire that might loose traction. This drives very smooth, and the car rotates very nicely in my Vanquish, even with standard gear diffs front & rear (with no heavy grease or shims).

A torque splitter (center one-way), allows the front wheels to freewheel in a turn, so they stay in contact with the road. This means the car is 4WD in a straight line, and 2WD in a turn. If the rear wheels do happen to loose traction in a turn, the front wheels will start to drive once the rears catch up. The overall result is more over-steer. Keep in mind that there is still a limited slip effect side-to-side from the front diff, even though the fronts are freewheeling. This can reduce front traction in a turn and counteract the over-steer. You also only have rear wheel breaks with this setup (which means over-steer on braking)...

A front one-way diff also allows the front wheels to freewheel in a turn, but the difference from the center one-way is that there is NO limited slip effect from left to right. This makes gives the car more over-steer, and a little more intense. Still no front brakes either.