Join Date: Sep 1999
Location: Hot Springs, AR
Thanked 5 Times in 5 Posts
Re: Matching Axles ratios front to rear
The difference in ratio has nothing to do with trying to get one axle to spin faster than the other. This is a reply I wrote on 8/13/00 and again on 4/29/02:
the front and rear axles usually have different diameter ring gears. sometimes this difference is why they have a different number of teeth. for example: a dana 44 4.09:1 ratio has 45 teeth on the ring gear and 11 teeth on the pinion. (ring gear diameter is 8 3/4"?) 45/11=4.090909... a dana 30 4.10:1 ratio has 41 teeth on the ring gear and 10 teeth on the pinion. (ring gear diameter is 7.5"?) 41/10=4.10. this little difference in ratios isn't enough to worry about.
This is from 12/02/02:
The reason the front and rear are different on many 4x4's isn't because one end is designed to "outrun" the other. The reason is very simple: they are usually different model axles. With different models, such as a dana 30 front and 35 rear, the ring gears are different diameters. That means that the teeth count probably won't be the same which is where the slightly different ratio NUMBER comes from. From a design view, 4.09, 4.10, and 4.11 for example, are the SAME. They are that close. Again, the difference is just due to the different diameter ring gears and pinion gears. That's all, nothing else.
The number of teeth on the ring gear is dependant on the diameter of the ring gear. Different diameters mean different tooth counts for the "same" ratio.