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Old 11-09-2010, 01:49 PM
  #35069  
SlowerOne
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Join Date: Jun 2005
Posts: 900
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Originally Posted by LonnyJ1950
My diff is free. it will turn against the drag of the motor. And the diff will do it's job even with a bit of drag. Spinning diffs are overrated. In most cases the only difference between a "free" diff and one with a bit of drag is a slight difference in rear bite, very slight.
In a class where tenths count because you're losing them for eight minutes, not five, very slight isn't good enough. A free, but slip-free diff is an essential component of a good handling 12th car.

Thrust races make the diff stiff and 'lazy'. There is nothing wrong with the ballrace used as a thrust race providing the diff is glass smooth and has absolutely no slip at all. They last much longer if you have a belleville washer between the nut and the thrust cone, as this takes the side knocks when you hit the boards.

I have run Corally thrust races for ages, and couldn't believe the improvement in turn in and power out from corners when I switched back to a ballrace. The ballrace must be very clean - no grease or oil - and then have one drop of synthetic oil in it to help with friction on the cage. Any grease or thick oil and the ballrace will slip, meaning you have to do the diff up tighter.

Here's the definitive diff-building advice from the man himself - Dave Irrgang.

http://www.teamirsrc.com/techtips.html

One last tip - make sure to use a steel ballrace, and not a ceramic one. The ceramic ones have to be done up tighter as they slip more due to the ceramic coating. HTH
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