Help Me With 5.13 Math... Re-Gear time

[SAF]

Hey, folks.

I decided my factory, non-XR with 37s and 3.73s is just too much of a dog and shifts way too quickly for my taste at light throttle around town. Whilst 4.56 or 4.88 seem to be the norm, I took it a step further and went with a 5.13 setup. They should be done tomorrow.

Apart from the 2.5" game changer, some upgraded shocks, the 37s, and an AEV bumper/tire carrier with spare, this thing won't be filled to the brim with gear or goods (for now).

So, given the ratios and say maybe an extra 100-300lbs of aftermarket products and about 200lbs from the driver, just how high will that 8th gear RPM be at say 70mph? I'm also not sure on the specifics of when the cylinder deactivation comes into play, but I'm hoping these higher engine speeds will help mitigate that with the 35-45mph zone (probably more likely to deactivate here since rpm will drop at a lower speed/not as much throttle)

Worst comes to worst I'll throw some 4.88s in it... or some 40s...

Thanks!

Edit: Running Cooper STT Pros which come in at roughly 36.7" if I'm not mistaken.

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[SAF]

I pulled the trigger on 5.13s a couple of weeks ago. Rubicon with RK 2.5, 37“ MT Baja Boss AT, and a few other upgrades… I can’t put into words how much better it is. I live in Denver, rpm at 70mph is just a touch over 2500. Acceleration and shifting is so much better.

392, right?

 

[Philip]

All depends on what you’re doing with your jeep. I have 2 392s so I have been able to compare 3:73, 4:56, and 4:88. Going from 3:73 to 5:13 will be a big bump in low-end but will cost you a bit in gas mileage. Based on your weight, 4:56 would have been my choice… but you’ll be very pleased with your low and mid-range speeds!

My big 392 weighs in around 7k, on 40’s and 1-tons. I went 4:88 because I have to balance off road and on-road performance. I would have gone with 5:38 if it were a trailer princess.

 

[sherpaJL]

Hey, folks.

I decided my factory, non-XR with 37s and 3.73s is just too much of a dog and shifts way too quickly for my taste at light throttle around town. Whilst 4.56 or 4.88 seem to be the norm, I took it a step further and went with a 5.13 setup. They should be done tomorrow.

how did the 5.13s work out?

 

[SAF]

how did the 5.13s work out?

Not bad at all. I won’t be driving this one on the highway for extended periods, but it definitely got its pep back. Rolling off the line, it jumps to 2nd gear almost immediately and it runs up to 8th gear even in the 35-45mph range, then the cylinder deactivation kicks in.
Before I was at about 14mpg but so far I’ve only lost about .5 mpg with city driving/brief highway runs.

 

[Philip]

Cool, about what I figured and I didn’t need a calculator ??

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