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post #1 of 4 Old 06-16-2001, 05:51 PM Thread Starter
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Location: Camino, CA
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I currently have a 1978 cj5 with an inline 6 with a T-18A 4sp and was wondering what the best gear ratio for the front and rear diff would be.

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post #2 of 4 Old 06-16-2001, 07:53 PM
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What size tires... what are you going to do with the Jeep? Rock crawling? Daily commuter car that never sees mud? It all makes a difference. If you want the daily driver fuel economy, I'd go with like a 3.07 or something... but if you're putting big mudders on it with plans to only run it on the weekends, go with something way more aggressive like 4.11 or 4.56.
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post #3 of 4 Old 06-20-2001, 02:49 PM Thread Starter
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I have 32x11.50x15 size tires. My other cj5 has the same size tires but it has 4.27 gears and a 304 v8. Currently the 1978 cj5 has 3.54 gears and seems a little high geared. I use the jeeps for hunting which finds on steep slopes and muddy roads. I do not do much rock crawlin. My 1974 cj5 has a crawl ratio of 53.9 in low 1st gear. and the 1978 has a crawl ratio of 44.7. Both have 32X11.5X15 tires. I was considering putting in a terra low gear set in the model 20 tc. and that would give me about 70 to 1 in crawl. what do you think.
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post #4 of 4 Old 06-28-2001, 10:11 AM
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I found this handy chart, I think it will answer your question. It gives you the formula for calculating RPM's for any speed based on tire size and gear ratios.

It's not so much a labor of love as it is shear determination.
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