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AJeepZJ
08-24-2011, 08:10 PM
I was looking for this chart a few days ago and found it.
https://theultimatejeep.com/images/imported/2011/08/gearratio-1.jpg

Generally, the acceptable RPM range is 2000 to 3000, which is represented by the entire shaded area of the chart. The optimum RPM range is 2300 to 2600, and it is represented by the green shading.
Sal-XK
08-24-2011, 08:14 PM
Was the test speed for this 60MPH?
AJeepZJ
08-24-2011, 08:16 PM
Was the test speed for this 60MPH?

55mph
Sal-XK
08-24-2011, 08:18 PM
Ok So to use this chart then you need to know what gear in the trans is running 1:1? or am I way off and should go to bed now.
AJeepZJ
08-24-2011, 08:21 PM
It's the gear ratio you see on the Y-axis: 1. For example the XJ has a 3:55 gear ratio and It is currently equipped with 33's. This chart essentially states it is just barely outside the highest efficiency zones. The top yellow shaded regionl, to my knowledge, is best for wheeling/crawling, the bottom yellow region is best for highway cruising, the green is the best compromise between the two. Hence your XJ crawls extremely well at Uwharrie (even without the lockers), But it has a hard time holding 65 on a slight up hill, lol. It would love a 3.73 or 4.10 gear swap.