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Discussion Starter · #1 ·
I was wondering if it is bad for the engine to be on the highway cruising at 70-80 mph in 4th gear. I would usually use 5th but if I come to a hill it goes right down to 50-60 mph. Usually the rom's are around 2,500- 3,000, thanks in advance for all of the help! I'm sure I'll have more questions soon enough!
 

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Yes you have to down shift depending on the conditions.
 

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I assume you are running larger tires than stock without a gear change. To answer your question running the Jeep in the 2,500 to 3,000 range from what I have read is fine. What u have read about is the 4.0 motor
 

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Discussion Starter · #4 ·
The tires I have now are 31, but I believe it is lifted and I do t know what gearing it has. How could I find out? Thank you for the info it makes me feel a bit better taking a 200 mile road trip in it during the summer.
 

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There might be a silver tag on your diff with the gear ratio on it but those usually get tossed when gear oil is changed. Your next option would be to jack up one rear wheel and count the number of times the driveshaft spins in one complete estriol of the tire. Just FYI RPM calculation is as follows:

RPM=(MPH*final gear ratio*336)/tire diameter

Final gear ratio=differential gear ratio * transmission gear ratio in a given gear. You can google the gear ratios for your transmission

I would say 3,000 RPM would be the top limit of where I would want to run the engine. As you know your gas mileage will be terrible at that RPM
 

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all your HP is above 3k rpm.. lol
 
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