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Posted by D Sherman [24.32.202.83] on Saturday, April 10, 2010 at 00:12:38 :
In Reply to: Axle ratio front to rear? posted by Glen Idaho [64.126.154.237] on Friday, April 09, 2010 at 23:17:35 :
I wonder why they built the difference in ratios into the differentials rather than into the transfer case. It seems to me it would make more sense to make the differential gears identical, front and rear, and handle the ratio in the transfer case where doing so wouldn't require making and stocking two sets of nearly-identical parts.
The old M35s with the automatic (sprag) transfer case have an 8% difference in ratio between front and rear, with a free-wheeling clutch in the T-case such that when traction is good both ends are turning at the same speed and the clutch free-wheels, but when the rear turns more than 8% faster than the front, it assumes the rear is spinning and it engages the front automatically. At that point, the front will turn 8% slower than the rear, which is opposite to the situation you're describing, but all the wheels more or less spinning anyway, it doesn't make much difference. They did eventually do away with the sprag, however, and went to a manually-locking T-case with the same ratio at both ends.