2011 JKURL gearcharts dont match my info
08-21-2017, 12:27 PM
#1
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2011 JKURL gearcharts dont match my info
Hello All,
I have a good question I think. I have been looking at posts all day on a gears. The gear charts that posts refer to are nothing like what I am running in my jeep as in rpms/tire size.
first off I have a 2011 JKURL, auto,3.8, 4.10 with 315/75 16's and the true measurement is 33.5 in they have some wear on them I don't know if they run this size new but still look good. I know that they are a BFG and they are heavy. this is a duel purpouse rig. I will be overlanding soon I run trails and hiway
my rig is turning 2500 rpms at 70 verified with traildash and yes I have the calibration set for the tires.
according to the chart this is what a 3.6 with a auto with 4.10 gears. I am confused.
which is causing me grief on what gear ratio that I should up grade to according to the 3.8 chart auto I should be in just over the 2000 rpm range. well at 500 rpm difference from one chart to the other you might see my concern for the gearing issue. the math is not adding up from my real numbers to the chart. I could understand 100 to 200 rpm but it is 500 and that is a big jump if even for 5.13 gears . I would like some clarification if possible.
I have a good question I think. I have been looking at posts all day on a gears. The gear charts that posts refer to are nothing like what I am running in my jeep as in rpms/tire size.
first off I have a 2011 JKURL, auto,3.8, 4.10 with 315/75 16's and the true measurement is 33.5 in they have some wear on them I don't know if they run this size new but still look good. I know that they are a BFG and they are heavy. this is a duel purpouse rig. I will be overlanding soon I run trails and hiway
my rig is turning 2500 rpms at 70 verified with traildash and yes I have the calibration set for the tires.
according to the chart this is what a 3.6 with a auto with 4.10 gears. I am confused.
which is causing me grief on what gear ratio that I should up grade to according to the 3.8 chart auto I should be in just over the 2000 rpm range. well at 500 rpm difference from one chart to the other you might see my concern for the gearing issue. the math is not adding up from my real numbers to the chart. I could understand 100 to 200 rpm but it is 500 and that is a big jump if even for 5.13 gears . I would like some clarification if possible.
08-21-2017, 01:58 PM
#3
I ran 4.88 for years, with 315's it's pretty close to stock performance. If I was still running 315's I would do 5.13's, if you plan on adding gear\ accessories for over-landing the extra rpms will help.
08-21-2017, 02:14 PM
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Ignore what I wrote earlier, if you caught it. I was looking at the wrong charts also...
Use the 3.8 charts. They have been accurate for my 3.8 auto through 3 different ratios and 5 different tire sizes.
Measure your actual tire height again (33.5" should be accurate, but doesn't hurt to double check it).
Compare your speedo/traildash to gps (the traildash just regurgitates what the computer tells it? which could be different than what a gps shows?).
OD was On, or Off at the time?
Have you verified that you have 4.10's? (If you ar ethe first owner, not likely that you have anything else for that year rubicon, but who knows what a previous owner might have done).
And just a shot in the dark, but you might try going back to stock on the traildash, then re-entering both tire size and gear ratio, and see if it makes a difference.
Use the 3.8 charts. They have been accurate for my 3.8 auto through 3 different ratios and 5 different tire sizes.
Measure your actual tire height again (33.5" should be accurate, but doesn't hurt to double check it).
Compare your speedo/traildash to gps (the traildash just regurgitates what the computer tells it? which could be different than what a gps shows?).
OD was On, or Off at the time?
Have you verified that you have 4.10's? (If you ar ethe first owner, not likely that you have anything else for that year rubicon, but who knows what a previous owner might have done).
And just a shot in the dark, but you might try going back to stock on the traildash, then re-entering both tire size and gear ratio, and see if it makes a difference.
Last edited by nthinuf; 08-21-2017 at 04:19 PM.
08-22-2017, 08:04 AM
#5
Jack up the rear, just one tire in the air.
Mark the driveshaft.
Have someone spin 1 tire 2 full revolutions.
Count the driveshaft revolutions.
This is your gear ratio...
Mark the driveshaft.
Have someone spin 1 tire 2 full revolutions.
Count the driveshaft revolutions.
This is your gear ratio...
08-22-2017, 07:27 PM
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Ignore what I wrote earlier, if you caught it. I was looking at the wrong charts also...
Use the 3.8 charts. They have been accurate for my 3.8 auto through 3 different ratios and 5 different tire sizes.
Measure your actual tire height again (33.5" should be accurate, but doesn't hurt to double check it).
Compare your speedo/traildash to gps (the traildash just regurgitates what the computer tells it? which could be different than what a gps shows?).
OD was On, or Off at the time?
Have you verified that you have 4.10's? (If you ar ethe first owner, not likely that you have anything else for that year rubicon, but who knows what a previous owner might have done).
And just a shot in the dark, but you might try going back to stock on the traildash, then re-entering both tire size and gear ratio, and see if it makes a difference.
Use the 3.8 charts. They have been accurate for my 3.8 auto through 3 different ratios and 5 different tire sizes.
Measure your actual tire height again (33.5" should be accurate, but doesn't hurt to double check it).
Compare your speedo/traildash to gps (the traildash just regurgitates what the computer tells it? which could be different than what a gps shows?).
OD was On, or Off at the time?
Have you verified that you have 4.10's? (If you ar ethe first owner, not likely that you have anything else for that year rubicon, but who knows what a previous owner might have done).
And just a shot in the dark, but you might try going back to stock on the traildash, then re-entering both tire size and gear ratio, and see if it makes a difference.
Yes, I have looked at the 3.8 auto charts and that is why I have this delima. if others are seeing the same approx. rps vs wheel size and gear ratio on that chart then there is something different in my jeep. I have not physicaly checked the tire rotation methoed to see if the 4.10 is close. but I have checked the speedo with my GPS and it is within 1mph. so I would think that the settings vs the tire size and gear ratio it should be a 4.10 but sense it doesn't match the 3.8 gear chart I am perplexed.
I have noticed one thing tho. some of the videos I have seen with people showing off there speed with different gear ratio's I looks like when the trans shifts into 4 lock the rpms drop approx. 2000 well on mine it only drops about 1500 to 1700 not 2000 of course it is alittle hard to tell I have to be on the gas pretty heavy.
the trans does not get hot and the traildash does show that I am in 4 locked(OD) trans runs around 150f it is sluggish in wind, hills I end up going 55 and then down shift to 2 half the time then 3 , 3lock, and then 4lock
I will probably try the 5.13's but I don't want 3000+ rpms. I guess if it is to high I will just have to buy bigger wheels and tires. sucks that 16" wheels have limited tire sizes
08-27-2017, 06:05 AM
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I still don't understand why I would be turning 2500 rpms with the 3.8 auto gear chart says I should be at 2017 rpm with 4.10 gears with the auto in 4th and locked converter and 33 tires. Especially when the gps is verified at 70 mph both dash and gps are within 1 mph
any thoughts
any thoughts
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08-27-2017, 07:48 AM
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Sounds to me like either someone has already swapped gears or your Torque converter is not locking up.
What RPM are you at when you run 70 with OD off. There should be about a 500rpm difference between OD on and off.
Before my gear change I ran 2100rpm at 60mph with OD Off, 3.73 gears, 35" tires. 1600rpm with OD on.
What RPM are you at when you run 70 with OD off. There should be about a 500rpm difference between OD on and off.
Before my gear change I ran 2100rpm at 60mph with OD Off, 3.73 gears, 35" tires. 1600rpm with OD on.
08-27-2017, 11:55 AM
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Just checked on the gear charts and if you in fact are at 2500rpm at 70mph and you know for fact that the trans is working properly I'm gonna say you already have 5.13 gears.
08-27-2017, 11:55 AM
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You have 'verified' that you have 4.10's? Or you're saying that just because the original build sheet listed them?
33.5" measured height with 4.10's = 1987.5 rpm @ 70
around 2880 @ 70 od/off
33.5" measured height with 5.13's = 2487 rpm @ 70
around 3600 @ 70 od/off
Divide od/on by .69 to get od/off (3rd gear). I have not seen a formula for torque converter locked vs unlocked.
33.5" measured height with 4.10's = 1987.5 rpm @ 70
around 2880 @ 70 od/off
33.5" measured height with 5.13's = 2487 rpm @ 70
around 3600 @ 70 od/off
Divide od/on by .69 to get od/off (3rd gear). I have not seen a formula for torque converter locked vs unlocked.