Re-gearing questions

SteveF

SteveF

U.S. Coast Guard Retired
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Eastford CT
In about a month I will be changing gears in my axles in my 2015 JKU w/automatic transmission. I am currently running 3/73's on 35" tires. So I have 2 questions. Roughly what should I be looking to pay. I will NOT be doing this myself. 2nd question is I was told that 4/10 gears may not be enough. I don't want to be doing 65mph at 3500 RPM's either. Any suggestions? I never had to do this with previous jeeps so I am totally in the dark here.
 
SteveF said:
In about a month I will be changing gears in my axles in my 2015 JKU w/automatic transmission. I am currently running 3/73's on 35" tires. So I have 2 questions. Roughly what should I be looking to pay. I will NOT be doing this myself. 2nd question is I was told that 4/10 gears may not be enough. I don't want to be doing 65mph at 3500 RPM's either. Any suggestions? I never had to do this with previous jeeps so I am totally in the dark here.
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From what everyone says about what to pay it depends on where you live. Best thing is to contact someone in a Jeep club and they usually will have the best references.

Also a 4.56 gear is what most will recommend, and also don't forget about the speedometer recalibration.
 
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I`m the same as @IndominusHuman I run 35`s and 4:10 and 65 around 2200 I can set the cruise at 70 and it will maintain speed and the ECO light still will come on. But if you are going to spend the money to regear I would go 4:56 just to get the better response on general driving
 
mrjp said:
I`m the same as @IndominusHuman I run 35`s and 4:10 and 65 around 2200 I can set the cruise at 70 and it will maintain speed and the ECO light still will come on. But if you are going to spend the money to regear I would go 4:56 just to get the better response on general driving
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Agreed. The price will be the same for 4:56 and 4:10s so why not just go 4:56.
 
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Sounds good to me. Now if I could only find someplace to take it to get it done.
 
I was told that 4:56 gears will get me back to what it would run like if it were completely stock.
 
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SteveF said:
In about a month I will be changing gears in my axles in my 2015 JKU w/automatic transmission. I am currently running 3/73's on 35" tires. So I have 2 questions. Roughly what should I be looking to pay. I will NOT be doing this myself. 2nd question is I was told that 4/10 gears may not be enough. I don't want to be doing 65mph at 3500 RPM's either. Any suggestions? I never had to do this with previous jeeps so I am totally in the dark here.
Click to expand...
2015 JK Sport, just went from 3:21 to 4:88 and at 80mph only 3k rpms....manual.
 
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I'm going to stay with the 4:56 gears. Just have to find a place to get it done.
 
So I decided to jack up the jeep to spin the wheels and driveshaft. I had both wheels off the ground and transmission in neutral. Something didn't go right or I did something wrong. As the driver side tire was spinning in the forward direction the passenger side was spinning in the reverse direction. But what I didn't understand was while the tire was being spun the driveshaft would rotate a little then stop then rotate a little more. One full turn of the tire and I didn't get a full turn of the driveshaft. So I tried it with only one tire off the ground. One full turn of the tire resulted in almost 1.75 turns of the driveshaft. So now I'm totally confused. HELP!!!
 
The driveshaft likely moved a bit because it was in neutral. If you leave it in gear or park, you won't see any rotation in the driveshaft induced by turning the wheel
 
I had the transmission in neutral so I could spin the tires. The driveshaft turned a little with both tires off the ground. With just one wheel turning the driveshaft steadily rotated but but only made 1.75 revolutions
 
Turn the driveshaft and see what you get after the tires spin once. This I believe eliminates issues with open / limited slip / etc differential.

To be precise in these measurements, make a chalk mark on the tire, and tape a string to the drive shaft.
 
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Thanks for the advice. I'll jack it up again and turn the driveshaft instead of the tire
 
So I just plugged my jscan tool in to see what the jeep says I have for axle gears. The build sheet says 3.73's but the jscan says 3.21's. I can't wait to see the difference when I get to installing the 4.56 gears.
 
I don't think Jscan reads what they actually are, but what is plugged in. I didn't even realize it had that function, beyond the ability to change the setting in the computer, a must when making that kinda change.

Use the vid above to actually determine what you have. If you have 3.73 and the computer thinks you have 3.21 I'm not sure what that would do.
 
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I jacked up the jeep and counted tire rotation vs driveshaft rotations. It is definitely 3.21 gears
 
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