You say the grease used in the ball diff makes the most difference, what different greases can you use on a ball diff?

There is no way to say this without sounding like a d*ck, but I would take dinorider's post with a grain of salt. A lot of the history is incorrect in my opinion or does not apply to a competition environment.

How spools got popular: Reedy Race outlawed oneways due to too many straight peels in braking zones...everybody tried spools and it was faster..

How to set a ball diff: Hold both wheels, and try to move the spur. If the spur doesn't move, it's tight enough.

Kyosho Spider or Yokomo YR4--- 1st 2 belt setup

Why a gear diff: 100% forward lock and you can set the amount of differentiation with oil or putty, etc. Almost as soon as the SC10 came out, dirt oval guys had gear diffs in their cars. (BTW MIP had a gear diff version of their RC10 transmission 20+ years ago, and they used it in dirt oval them, too.) I tried one and i loved it. As soon as I heard Spec R was making them for touring cars, I got the diffs.

A properly set ball diff still slips a little. I saw it as soon as I put the gear diffs in. I was always rear ending cars on main starts. Today's brushless power has so much torque, it makes a lot of sense to use a gear diff. Yet, a lot of guys still like ball diffs.

BTW the mini cars often use gear diffs filled with putty or plastic wrappers. I have seen this for a while. They still want a very small amount of diff action. Otherwise, they would just bolt the diffs together for a spool.

Probably works fine for a Silvercan setup :lol:

Personally history to me is just that. A reference point in time that we can learn from, but doesn't necessarily apply to todays options.

I (and most IMO) want what works best today given our priorities whether they be cost, speed, low maintenance or what have you. Each person has to set his priorities and decide. IIRC the OP said he never tried a spool, I find that odd yet found some useful info I will try, or had planned to anyway, but advising against it would be kinda silly without REALLY knowing.

I like a spool, I like a ball diff, and I plan to try the gear diff and decide. I'm sure each has their place, and track, and car they work best in, but for the cost of a set of tires why worry about history when you can decide whats best for your conditions. :cool:

Got to agree with this...

TA03F Pro was the first TA03 car Tamiya came out with and had a ton of on power steering because the motor was IN FRONT of the FRONT wheels. All that weight really helped keep the front tires pulling on power. (I owned one and loved that about that car...something to think about.) The gearbox/belt layout was comparable to the setup of the new SC10 4x4 by Associated...with the exception of the motor's position obviously.

The first RS4 was a gearbox rear transmission with a top shaft that transfered power to a front belt and to a front diff. Later a dual belt conversion kit was released that allowed you to convert the car to the traditional 2-belt layout we all know now. (STILL own an original RS4 and outfitted it with the dual belt conversion early on.) Kyosho had a very competitive dual belt car and Yokomo came out with another that prompted the dual belt trend.

Most importantly there was another aspect of this write-up that needed to be addressed, the front on-ways. It was not uncommon to run TWIN one-ways...a one-way front pulley AND a one-way front diff. The theory was that the one-way front pulley would allow you to take the resistance the mass of the front drivetrain would rob from the power being able to be delievered to the rear tires thus giving you greater acceleration and top speed. The front diff was retained so that if you lifted the inner front wheel off the ground or it started scrubbing, the outside wheel would still recieve full power.

The main issues with one-ways was weight and durability. They tended to weigh more than ball diffs and the bearings could be damaged in an hard wreck and thus ruin the expensive one-way unit.

In Super Nitro racing I use to race with a rear diff that ran very thick oil and a front one-way differential. Braking was a touchy subject but the front one-way provided so much turn in that you could maintain a lot of speed entering a corner and thus didn't need a lot of braking with the setup.

As was mentioned though setting up a ball diff, and making it smooth, was a task that could only be done if someone showed you what "right" and "smooth" was and took a great deal of trial and error.

By contrast, modern gear diffs are designed to be sealed, filled with fluid and bolted together. No "training" is necessary and the only trial and error is trying to figure out what fluid to use to get the appropriate diff action. If today's proliferation of RTR "kits" is any indication, the current R/C market favors things that require very little "tuning knowledge" to setup and gear diffs certainly fit this description. Ball diffs just no longer make sense and their bennefits no longer fit with current technology.

That part of dinorider's post was spot on. Ball diffs served a purpose (and maybe with 1/10th scale pan car oval still do) but with today's high powered brushless setups, slipper clutches, and other advances the reliability and ease of use of the modern gear diff makes it a better option.

If Rick is willing to come on here and give advice, take it. The front gear diff tech emerged at the 2011 Reedy race and worked well for guys finishing up front. Just a fad I guess like Abercrombie shorts.

Not sure if I would call it a fad, Martin and some other XRAY Euro drivers have been running a front GD for a while now. Heck if I'm not mistaken they were the 1st to run putty in it.

If you are running 500k in front gear diff what are you running in rear gear diff?

Old thread, but it led to some interesting reading at the time and I find myself coming back to it today...

How can you tell if your rear (gear) diff is unloading? And if it is, is the problem with the fluid inside the diff itself or is it a bad setup causing the issue (or a bit of both, of course?) Which part would you address first in an attempt to fix this?

Probably be snappy loose on exit. If the diff is unloading you are obviously breaking traction at the unloaded tire because there is not enough load at that point in the corner to begin with. Solve the setup issue, but consistancy in your equipment is key to deciphering your driving and/or setup problems. Just my 2 cents.

I think the unloading is subjective to setup, and how you drive, I know many guys run super thin oil, which plants the rear end almost regardless of setup, but I have seen and driven setups where it's a tighter rear, steered with the help of the back ends ability to come out some.

Tricky balance it is with the rear diff. If the oil is thin it allows car to turn easier, more off power steering. On exit it plants the rear providing more forward bite, which might lead to push.

Tighter rear diff will resist entry to the turn, a bit less entry steering. Its not always a bad thing. A smooth, progressive entry to the corner can assist mid corner speed. On exit there is more steering as the rear slips sideways more on exit with a tight diff, and therefore gives less forward bite.

Its all connected to how the car transfers its weight to each corner during the different phases of the turn, and the diff plays an important part

Quite important to get this right. In general I prefer to set for my personal driving style rather than to adapt the setting for the track

There's only a limited amount of traction available at each corner of the car during each phase of the turn and you've got to decide how to use it best, whether you need edge grip or forward bite, its a constant trade off

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