Gear v Ball Diff

[MatJohnson]

All these new fangled geared diffs like the ones on the durango. What advantages do they offer over a 'normal' ball diff to 1/10th use?

Is it just reduced maintainance or is there an advantage to using the geared diffs?

Can't find the answer in a sensible format anywhere

[smokes]

Basically ball diff act like an Limited slip diff on an road car how much slip depend on how much you tighten the diff. With the gear diff it act like and open diff as soon as on e wheel lift of the ground the power goes to the unloaded wheel. With modern tooling and seals we can now use heavy silicon fluid to stop the gear diff unloading to the undriven wheel.

The only difference is the weight of the gear diff means if has more inertia to over come than a ball diff, hence it slower to accelarate, but with the torque of a brushless it is not noticable.

But the gear diff won't slip when accelarting in a straight line like a ball diff will due limit of how tight you have the diff plate before it flattens the balls and stops it working.

how it feels i don't know as i haven't used a fluid filled gear diff yet.

[RogerM]

Gear diffs Vs ball diffs

Advantages:-

1) don't slip and can not come undo during a run (although the seals can give up and the oil empty changing the feel)
2) a definite adjustment, 10 people build 10 diffs with the same brand of oil all will feel almost exactly the same .. 10 people builds each build a ball diff your likely to get 10 different feelings ... makes transfering / recording set-ups easy

Disadvantages

1) weight (not too much of a problem these days)
2) limited steps to the adjustment (whatever the oil weight steps are)
3) longer to adjust (have to dismantle the car, depending on design that can be a PITA .... trust me .. not something you want to be doing 5mins before your run)
4) messy to adjust (trust me .. not something you want to be doing 5mins before your run)
5) can make one hell of a mess if a seal goes ... usually a full strip down to get everything washed clean!

I've run with both types (in both 1/8th and 1/10th as I am old enough to remeber the geared diffs in 1.10th Kyoshos & Tamiyas and ball diffs in 1/8ths, mainly on-road) and to be honest if I was designing a competition car these today I'd use ball diffs in 1/10th but geared in 1/8th (purely because they 1/8th cars put a lot of load on a diff and ball diffs are harder to make stand such loadings.

[Chris Doughty]

2) limited steps to the adjustment (whatever the oil weight steps are)


- really!? so I can't add one drop of another weight of oil to the diff and change it by the tinyest amount imagineable?

[RogerM]

Indeed you could if you wanted to but I'm not sure that many people would want to and you would also loose the advantage of transferable / repeatable set-ups.

I ended up with several sets of diffs built with different oils in when I was running 1/8th off road as I hated the mess and risk of getting dirt in them.

I get your point though Chris, but it's still easier to tweek the ball diff. Both have their uses, I guess it's like so much in this sport .. where there is a choice to be made personal preference will dictate that choice, no right or wrong

[Chris Doughty]

have you forgotten the days of the Losi team writing on their setup sheets about running 25wt oil with 4 drops of 30wt?

big drops or small ones?