Ball Diff or Gear Diff?

[whites75]

Being pretty new to hobby I wondered is there was any pro's or con's of running with a ball or gear diff and which is the best option to go for?

My bmax2 has the gear diff as per kit but I have noticed others using ball diffs in theirs and wondered why?

Cheers
Phil

[DynaMight]

Most people seem to prefer the ball diff.

The general rule of thumb is gear diff is better for high traction like carpet/astro but ball is better for low grip, but like I said, most of the top drivers in my area tend to prefer ball diffs for every type of surface.

I recently ran a gear diff & ball diff back to back (thanks to the shafts popping out on the DEX210) and I could tell straight away that the gear diff seems to push the front wider when putting some power down mid corner & also the rear snapped out alot easier when hammering it out of corners.

[vrooom]

Depend what fluid in it.. Gear diff is build once and forget, where ball diff need regular maintence.

[Dkfream]

I have ran my B5m with both gear and ball diff, ball diff deffo better feel and more controllable but I always struggle with them and forever rebuilding and replacing balls, I can't make them last for some reason, then noticed how free the ball diff was compared to the gear diff, tried lots of different diff oils but they all seem so gloopy and thick, so out of a moment of madness I stripped my gear diff and filled with 30wt shock oil( yes very strange ) but now feels and handles exactly the same as a ball diff but no worries of slipping or turning the balls square, ran it on carpet and slippy gym floor and works perfectly so gonna stick with it for a while but looking good so far ........ Have ordered some new ceramic balls for yet another diff rebuild to have incase I feel like a change lol

[Xracer]

In theory there should be no difference, no pun intended!
A gear diff cannot slip under load whereas a ball diff can due to the very small contact patch between each ball and thrust plate, they are lubricated too!
The reason they 'feel' different when driving is because the ball diff IS slipping even when tightened down hard, the evidence to this is the maintenance required to replace the washers due to 'grooving' and pitting and the balls because they have become micro-faceted from slipping.
Using ceramic balls prolongs the ball life but the rings still suffer!
The initial tightening down also initiates pitting of the rings as they are relatively soft compared to steel and more so with ceramic balls.
It was interesting when discussing gear diff oil viscosity with a Schumacher member recently that they had reduced the recommended viscosity dramatically from their original build instructions to get closer to the ball diff handling 'feel' but of course a gear diff can never feel the same.
So it is down to preference when driving along with the acceptance that maintenance will always be the bane of the ball diff if this is the choice!

[SlowOne]

A ball diff will always be freer than a gear diff as the gears have to run on shafts and will have friction due to the gear bearing on the shaft. The shafts will 'twist' in the plastic housing due to the loads put on them by a heavy car, a lot of power and quite a bit of grip, especially on grass and astro. and, lastly, there is the friction from four gears imperfectly made rubbing each other.

However, because the ball diff will not be that free for that long (See post above from Xracer) it should be possible to make one feel like the other. The tighter the diff is, the more the tail of the car will slide - drift cars have locked diffs to make then slide! - so the more grip the track has the tighter the diff can run. That's one of the problems with a ball diff, it isn't that adjustable for grippy tracks.

It's not my class, but when I did run off road I wish the manufacturing capabilities could have produced a decent gear diff. If I did go back into it I would certainly try one over a ball diff. HTH

[AntH]

In theory, I think there should be a difference. If you were to try and characterise the 2 different types of diff by rotating one input at a variety of speeds and then measuring the torque to turn, they would be quite different. The balls diff would give a reasonably constant torque regardless of input speed. Not so with the gear diff due to the nature of the viscous friction... The torque would rise with input speed. This is the main reason for the difference in characteristics IMO.

Originally Posted by Xracer

In theory there should be no difference, no pun intended!
A gear diff cannot slip under load whereas a ball diff can due to the very small contact patch between each ball and thrust plate, they are lubricated too!
The reason they 'feel' different when driving is because the ball diff IS slipping even when tightened down hard, the evidence to this is the maintenance required to replace the washers due to 'grooving' and pitting and the balls because they have become micro-faceted from slipping.
Using ceramic balls prolongs the ball life but the rings still suffer!
The initial tightening down also initiates pitting of the rings as they are relatively soft compared to steel and more so with ceramic balls.
It was interesting when discussing gear diff oil viscosity with a Schumacher member recently that they had reduced the recommended viscosity dramatically from their original build instructions to get closer to the ball diff handling 'feel' but of course a gear diff can never feel the same.
So it is down to preference when driving along with the acceptance that maintenance will always be the bane of the ball diff if this is the choice!