Modified CJ3B gear rario -
  • 1 Post By amelovi
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post #1 of 6 Old 05-25-2020, 12:52 PM Thread Starter
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Modified CJ3B gear rario

Hi, I'm Amedeo. I'm an Italian overlander. In the last few years I used my Cj3B to travel across Asia especially around Central Asia, Iran, Afghanistan, Iraq, Turkey, Pakistan and India (@backtofrico if you want on instagram). In the past I already modified the Willys with an AMC150 engine and the ax15 (with Dakota bellhousing).
This year I modified the frame and swap to a 4.3 GM TBI engine and YJ leaf spring.
Now I have the amc20 with one piece axle and 3.73 gear ratio and 32 inch tires (265.75.16) however I would like to change the gear ratio and I don't know which one to use between 4.56 and 4.88.
Usually the countries where I go are high mountains (up to 5000m in lots of mountain passes) and with my flat fender jeep I never go up to 130km/h and there are very few highways and I'm cruising around 100/110 km/h usually.
Could you suggest me what to use base on your experience and not something about just a calculator?

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post #2 of 6 Old 05-25-2020, 04:22 PM
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Your AX15 is not too different from my T5...I run 4.56 gears and 35" tires and it's just right on the road and on the trails.
I also have an LJ (TJ Unlimited) with a NSG370 running the stock 3.73 hears and 33's, it could use 4.10's.

I think 4.56 would be too deep for your 32's, and 4.88's would be out of the question, unless you never drove it on the road.

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post #3 of 6 Old 05-25-2020, 06:51 PM
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I agree with stripperguy. 4.10's with 32's and an OD transmission might be a good choice.

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post #4 of 6 Old 05-26-2020, 05:16 PM
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Originally Posted by jeepdaddy2000 View Post
I agree with stripperguy. 4.10's with 32's and an OD transmission might be a good choice.
I run 4.10's and 32's with a T-176. It's ok for the short distances we drive here but I think things would be perfect with a 5th gear.
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post #5 of 6 Old 05-26-2020, 05:49 PM
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What makes you think you need a 4.56 or lower ratio? Seems like 4.10 would be as low as you would want based on your travels. If your 3b is light weight and on 32” tires, on a first gear ratio of 3.83, I would think you would be just fine. The most important and overlooked factor in gear ratio decision is the transmission first gear ratio and power to weight ratio.

I think with your lower than average first gear AND overdrive, with an improved power plant from a low powered 4 banger to a mild V6 you should be fine with something higher geared than 4.56.
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post #6 of 6 Old 05-27-2020, 12:33 AM
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I have a Willys as well but have not changed to so much more power.

My Willys has 4.27:1 axle ratios and runs on GOODYEAR CUSTOM XTRA GRIP which are tall and narrow and have a special tread pattern that makes the Hi-Miler Xtra grip capable of gripping in all weather conditions and our bad roads. They look really good on a Willys and have a 32" diameter.

The AX15 5th gear is 0.79:1, which is a good overdrive gear to have. 3.83:1 first gear is much lower than the 2.79:1 in my Willys.

If I was looking at cruising at 110 kph (70mph) in 5th gear I would be happy with 4.10:1 gears, the overdrive would keep the engine speed down.

On steep trails I know from experience that the 4.10:1 gears and the AX15 will ensure you have no problems, it is a very light vehicle and that is some deep gearing.

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