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Wheelers used to install much higher ratio (axle ratios explanation) gears in their axles to gear down and get better off road performance. But this would also adversely affect his on-highway performance. Since a serious wheeler will be installing significantly larger-than-stock tires in most cases, some change in axle gearing to correct for this and maintain good drivability is usually in order. However, it is not practical to lower axle gears alone to get low enough gearing for rock crawling, and if you did you would also mess up your gears for comfortable highway driving. Like you are stuck in second or something. Set your axle gearing for a best compromise that includes highway driving, if you are not planning to trailer the thing everywhere. For good highway driving with a V8 and 33 inch tires, I prefer about 3.73 to 4.11 ratio in the axle. The 3.73 is most comfortable without overdrive. With the 4.11, this means about 3000 RPM on the tach at 65-70mph. An overdrive drops this to the 22-2400 RPM range, which is real sweet. If we liked 4.11 with 33s, I would go 4.56s for 35s and 4.88 for 38s, and so on. These numbers work well with a torquey engine: Most V8s, as well as the Jeep 4.0 straight 6 fit into this class. 4 bangers and the 6 cyl motors meant to make their power at higher RPM will work better if you go up on the axle ratio: 4.56 for 33s, 4.88 for 35s, etc. Now these are good street ratios. If your vehicle rarely or never drives any distance on the road, you might want to use significantly deeper axle gearing. Other problems with overly deep axle gearing include the fact that as the numerical ratio gets higher, the pinion gear in the differential gets smaller. As it gets smaller, it gets progressively weaker. 4.88 or 5.13 ratios are usually considered the limit in most stock axles. return to your place in "Systems Approach to 4WD Gearing"article |
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