Talk me out of 4.88 re-gear

Overdrive for your specific transmission?

The point here is that this is a fairly simple math problem. And gear ratios are not very mysterious. A stock JK ran various gear ratios for it's tire andt transmission combinations. Knowing what those were is a good starting point for deciding what to choose for a larger tire.
I see what your what saying. Good point
 
Be careful of the charts. Does it include the overdrive ratio?

What does a stock JK run for rpms at 75mph?
if we went by the way the factory set mine up, it would be;
32" tire
1:1 4th gear = 70 mph @ 3014 rpm
0.83:1 5th gear = 70 mph @ 2501 rpm
 
Now we are getting somewhere.

NAG1/4.10/31" = 2766rpm @ 75mph
NAG1/4.56/31" = 3077rpm @ 75mph
NAG1/4.88/31" = 3293rpm @ 75mph
NAG1/5.13/31" = 3461rpm @ 75mph

NAG1/4.10/34" = 2522rpm @ 75mph
NAG1/4.56/34" = 2805rpm @ 75mph
NAG1/4.88/34" = 3001rpm @ 75mph
NAG1/5.13/34" = 3156rpm @ 75mph

NAG1/4.10/36" = 2382rpm @ 75mph
NAG1/4.56/36" = 2649rpm @ 75mph
NAG1/4.88/36" = 2835rpm @ 75mph
NAG1/5.13/34" = 2981rpm @ 75mph

Based on a stock JK with 32" (closer to 31") tires, NAG1, and 4.10 gears, the appropriate gears for 35s looks to be 4.56 minimum; for 37s looks to be 4.88 minimum.
 
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Grimmjeeper.com is a gear ratio calculator. Your transmission is the Dodge WA580/NAG1. Your true tire size is the center height of your hub from the ground x2.
his gear ratio currently is 3.21:1
not sure what the factory tire size was for his model
Now we are getting somewhere.

NAG1/4.10/31" = 2766rpm @ 75mph
NAG1/4.10/31" = 3077rpm @ 75mph
NAG1/4.10/31" = 3293rpm @ 75mph

NAG1/4.10/34" = 2522rpm @ 75mph
NAG1/4.56/34" = 2805rpm @ 75mph
NAG1/4.88/34" = 3001rpm @ 75mph

NAG1/4.10/36" = 2382rpm @ 75mph
NAG1/4.56/36" = 2649rpm @ 75mph
NAG1/4.88/36" = 2835rpm @ 75mph

Based on a stock JK with 32" (closer to 31") tires, NAG1, and 4.10 gears, the appropriate gears for 35s looks to be 4.56 minimum; for 37s looks to be 4.88 minimum.
I would agree, if the OP was going to go to 35's 4.56's are appropriate.
 
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So mine stock is 3.21 but I couldn't tell you orginal tire size unless I get the window sticker from the dealership. It's a sport s
 
his gear ratio currently is 3.21:1
not sure what the factory tire size was for his model

I would agree, if the OP was going to go to 35's 4.56's are appropriate.

Knowing what I know from elsewhere, I would have to wonder why pushing the rpms closer to 3k at 75mph is a bad idea. Do JK owners suffer from the same problem of lugging their engines as TJ owners do?
 
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4.56 and 35's it will be. Should I still sleeve and gusset the inner C's for strength on the Dana 30 til I can upgrade?
 
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Knowing what I know from elsewhere, I would have to wonder why pushing the rpms closer to 3k at 75mph is a bad idea. Do JK owners suffer from the same problem of lugging their engines as TJ owners do?
no the 3.6 has good power, even though i didnt regear when i went to 35's the ProCal module allows you to reconfigure shift points for your set up and recalibrates the speedo.
 
no the 3.6 has good power, even though i didnt regear when i went to 35's the ProCal module allows you to reconfigure shift points for your set up and recalibrates the speedo.

That helps some. The middle gears should be good, but the 1st and last are the most effected.
 
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4.56 and 35's it will be. Should I still sleeve and gusset the inner C's for strength on the Dana 30 til I can upgrade?
I ran 35's on a D30 for years with no extra work done to it, albeit the JKU is much heavier than my TJ. After all Jeep has learned from the JK's predecessors, I dont think they would have kept it if they thought it wouldnt handle a 35.

to your question, dont waste your money beefing it up if youre going to upgrade to a D44
 
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I ran 35's on a D30 for years with no extra work done to it, albeit the JKU is much heavier than my TJ. After all Jeep has learned from the JK's predecessors, I dont think they would have kept it if they thought it wouldnt handle a 35.

to your question, dont waste your money beefing it up if youre going to upgrade to a D44
That's the thing though. The upgrade is literally years away. I do want to off road a bit, not rock crawl but two tracks and gravel roads. I don't abuse my rides. My cj is still on stock AMC 20 with two piece axle shafts and 33's. Dana 30 still enough for 35's and my style of driving? I appreciate all of your responses,this has been very helpful