J-Scan settings

SteveF

SteveF

U.S. Coast Guard Retired
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Jan 31, 2021
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479
Location
Eastford CT
So when I re-geared to 4.57 gears I went into jscan and entered my new gear settings. My tire settings are correct as well. But from the day I bought my 2015 Jk it seems like the transmission holds longer than it should before it shifts up to the next gear. It seems to only happen when going from 3rd to 4 or 4th to 5th. It downshifts just fine when climbing a hill. Is there a setting on Jscan that could be causing this. It's been doing this before and after the re-gearing so that wouldn't be the cause. My speedometer is off by 1 mph according to my Google maps app.
Any suggestions?
 
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SteveF said:
So when I re-geared to 4.57 gears I went into jscan and entered my new gear settings. My tire settings are correct as well. But from the day I bought my 2015 Jk it seems like the transmission holds longer than it should before it shifts up to the next gear. It seems to only happen when going from 3rd to 4 or 4th to 5th. It downshifts just fine when climbing a hill. Is there a setting on Jscan that could be causing this. It's been doing this before and after the re-gearing so that wouldn't be the cause. My speedometer is off by 1 mph according to my Google maps app.
Any suggestions?
Click to expand...
You need to put the physical diameter of your tires and not just say 35". Measure your tire with a tape measure. So your 35 might measure 34.25. Enter that number. That's how I fixed mine.
 
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Seems to me someone else recently had the same or similar issue. If I remember correctly, this individual reset tires and tranny back to stock. Reprogrammed for the gears first, then programmed for the tires.... or vice versa. For some reason, doing one before the other did make a difference.
So, what I would suggest is resetting the tranny and tires back to their original configuration, then program the new gears followed by the tire size.

(As Jeezy said, measure each tire height to within a quarter inch, add all four and divide to get the average to the nearest quarter inch- this is the most accurate)

Sorry, can't remember who here had almost the same experience.
 
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UPDATE!
So I put a level across the top of my tires and measured the distance to the ground. The tires setting was 1/2 inch too tall. So I adjusted the setting in Jscan to read 33.75. My speedometer is spot on with Google maps. My transmission is shifting better too.
 
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SteveF said:
UPDATE!
So I put a level across the top of my tires and measured the distance to the ground. The tires setting was 1/2 inch too tall. So I adjusted the setting in Jscan to read 33.75. My speedometer is spot on with Google maps. My transmission is shifting better too.
Click to expand...
Thanks for the update!
 
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SteveF said:
I don't object to a manual transmission but my better half doesn't know how to drive a stick and doesn't really want to learn, so automatic it is.
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Funny, my wife can not drive an automatic (we have been stick drivers for over 45yrs). Our JK was down for a week one winter, and she borrowed my Ma's Honda Fit. kept hitting the brake with her left foot.
 
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