Gear v Ball Diff
 

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 :)

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.

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.

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?

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

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? :woot:

LOL ... I had actually ... crazy times!

You are forgetting the critical one:

Gear diffs are currently fashionable.

Whether they really prove better only time will tell but for now the scramble for them is mostly because they are 'in'.

The main plus for me is I get more time to spend with my little girl at home as I'm not rebuilding nasty ball diffs all the time :thumbsup:

G

Ta all, was just wondering why the trend is to goto geared diffs. Seems they don't offer much of a performance advantage on 10th cars. Perhaps over summer they will show why we should all move to geared.

Build them right and you can have almost as much time :p

Although, i too now have a couple to test. Will update once i get the chance to try.

As controversial as it may be...I heard a nice lil rumour recently from a source I trust who said that even Durango were regretting using the geared diff in the DEX cos they think its wanky?

Just thought id throw that in :)

I thought the gear diff in the sc10 was wanky and wanted to stick a t4 ball diff in it - but the power that be said NO

I thought that you answered to no man?
I thought you were a Welshy Chuck Norris?
I thought were in a league with God himself?

Now you're telling me that someone said "no" to you and you let them live?

*crys*

Not sure where youve heard that from but as a Team Durango driver i think geared diffs are a fantastic idea!

I can change diff oils on tne Durango in under 10 minutes and when built correctly they stay leak free. Theres absolutely no slip in the diffs which gives you awsome acceleration, and the fact you can change oils so quick gives you excellent tuning options.

I know you can tighten or loosen a ball diff but doing this is no where near as consistent as changing oils, plus if you loosen it too far the diff will slip, or tighten it too far and you run the risk of putting too much pressure on the balls causing them to wear away quickly, again not a problem with geared diffs.

Big thumbs up from me :thumbsup:

All i know is when people asked me the set up for the sc10 i put down- gear diff- with lots and lots and lots of black greese fitted with part number #7678

they handle todays power levels better, asier to build consistently and have no slip no matter how loose you run them, since the "early or 1sr gear diff's" there easier to remove and are sealed

same for me from that lot

You also got to add, that they affect handling and balance a lot more under acceleration and braking, as it is a heavier mass to start rotating and stop....

http://www.youtube.com/watch?v=xlFquWZ3Lf8

there is not a great deal of weight difference, some where on here the weights were posted

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Yeh i agree they affect handling but in a positive way in my opinion. More rotating mass pushes the car down, thus generating more traction. The same goes for breaking, which is why the breaks on the Durango are second to none! Metal gears also ensures you dont have to worry about stripping gears under hard breaking or when accelerating hard out of a corner.

Again a big thumbs up from me :thumbsup:

I'm not sure where the idea that a ball diff is limited slip comes from. It isn't. There is no mechanism to apportion torque across the axle based on differential speed of each wheel. In a geared diff with silicon oil, there is the viscosity mechanism to allow some control of differential wheel speed across the axle, without the final lock-up that a Torsen or Ferguson diff gives.

If you tighten a ball diff, all you are doing is increasing the amount of differential axle speed needed to make the diff work. Once working, it won't then change its action if the differential axle speed changes. In many cases, it will 'break' abruptly, and then re-engage abruptly, something the silicone filled geared diff doesn't do.

Overall, it would be a geared diff using silicone oil that more closely approaches the usual definition of limited slip, and not a ball diff. I can't contribute to the weight debate, or the rotational acceleration requirements of a modern buggy. If I tell you that the last competitive buggy I raced was the 1994 Losi XX, and it's still sitting on my shelf in the shed, you'll see why!! HTH :)