Quote:
Originally Posted by rhbmcse
Why do people go thicker when the back end is loose?
I'd have thought in that situation you'd want the diff to give more rotation, hence thinner.
Clearly Im wrong but this seems to go against my logic.
Anybody explain?
Cheers.
Rob.
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I don't race touring cars, but my experience with rear gear diffs in buggies on polished floors is certainly thicker is better upto a point.
With light oil, in a corner, all the drive goes to unloaded wheel resulting in it spinning up which causes the car to over-rotate, spin out or fishtail depending on the nature of the corner and where traction is lost. Using a thicker oil combats this, and helps to keep the axle more locked and the drive more consistent to both wheels in the corner. Too heavy and the axle is fully locked, which does result in traction being lost as the wheels can not rotate at different speeds (loosing the diff action).
Going back to a ball diff setup (with a 2wd or 4wd buggy), I would normally run a tighter ball diff in a low traction situation, so this theory carries through to a gear giff setup. It's hard to replicate the feel of a ball diff with gears/oil, and some may prefer the ball diff (over a gear diff) in a low traction setting.
On the polished floor tracks I run at, with yokomo diffs I find in 2wd 3000cst-5000cst the right spot, and 7-10k cst in 4wd. The size of the diff, diff gears and volume for oil will also dictate what oil is best for you. You need to experiment to find it, but I'd avoid starting with too high or too low weight oils.