Here's my story of diffs. Based on experience from Touring Modified, R/C drifting, fullsize drifting with an RX7, rallying in an old Volvo and racing with a Formula First
Open diffs are never a good thing. It's makes a car quite unpredictable and unprecise. For a full size drift car it means unpredictable and unprecise entry, full unloading and the mother of all pendulum comebacks when the diff unloads and your outer wheel finds grip. For rallying it's that, plus that you lose a lot of forward grip and corner speed when it's unloading all power to the inner wheel, and the same thing goes for R/C drifting and Formula First.
Wheelspin = Unloading = Death.
And heres my first point. ALL 10th SCALE R/C CAR GEAR DIFFS ARE OPEN DIFFS!! At least so far. You can slow down the movement by adding thicker oil or lube, but the movement will never be predictable, it will never truly limit slip.
This winter I've missed clipping points, hit curbs and F****d up several runs without getting my mind around it. I even started to lose faith in my driving. I have always tried to be tight on my lines, and I have previously been very good at it, but this indoor season i've been terrible, and it got me thinking lots.
No matter how cleanly I turned into a corner, I really never made a clean even clip every lap. I turned in on the same spot, washed out, and ended up two feet from the curb. Next lap, same line, hit the curb and rolled over.
Why?
A gear diff never really works similar each lap, and while coasting into a corner it loads-unloads-loads-unloads, and same while braking into a corner. You could as mentioned put in a higher viscosity oil, but this will only be a compromise, as it would fuck up the things you do like. You want a smooth diff that doesn't do unpredictable stuff.
It's called a ball diff. The ball diff has a preset load, and if it's in good shape, it's as predictable and smooth as nothing else out there.
This is also my experience from my Ovlov rallycar. As soon as I got a true LSD in it, slowing it down and balancing it with engine braking through the gears worked brilliantly, and on power you just have so much more forward traction.
On my XXX-CR, the gear diff didn't really give anything forward until I was done cornering and both wheels had equal load. Damn, it was a rocket from then on. But still an unpredictable rocket
