Unsure what gears i have
05-29-2016, 05:13 AM
#1
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Unsure what gears i have
So I bought my 2015 JKU Sahara brand new last year. I didn't realize it that day but noticed later on the window sticker that it says it came with the dreaded 3.21 gears. To me it never seemed to perform like people say they do with such tall gears. I recently came across the chart that shows engine rpm based on gear ratio and tire size. According to the chart I should be turning just over 1800 at 70 but I'm turning just over 2100 at 70 which matched up for the 3.73/32" gear and tire combination. So after my long winded story my question is. How can I find out for sure what gears are in my jeep?
05-29-2016, 05:55 AM
#2
Super Moderator
To be sure, just download your build sheet. You can go on the Jeep website, enter in your VIN and it will provide you your build sheet. On the build sheet it will list the gear size your JK was built with.
Go Here to enter in VIN and get build sheet.
https://jeep.custhelp.com/app/jeep/e...WGxOMmc2T2w%3D
Go Here to enter in VIN and get build sheet.
https://jeep.custhelp.com/app/jeep/e...WGxOMmc2T2w%3D
05-29-2016, 07:32 AM
#4
JK Junkie
Chock the front wheels, put it in neutral, and jack up one rear wheel.
Make a mark on the tire and drive shaft.
Spin the tire 2 full revolutions while counting the drive shaft revolutions.
~3 and a quarter turns = 3.21s.
~3 and three quarter turns = 3.73s.
Make a mark on the tire and drive shaft.
Spin the tire 2 full revolutions while counting the drive shaft revolutions.
~3 and a quarter turns = 3.21s.
~3 and three quarter turns = 3.73s.
Last edited by 14Sport; 05-29-2016 at 07:38 AM.
05-29-2016, 11:32 AM
#5
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Did you measure your tires before plugging the height into the chart? I would imagine that your stock 32's are probably closer to 30.5" or 31" or something.
The 'spinning the tire and counting driveshaft revs' method works great.
The 'spinning the tire and counting driveshaft revs' method works great.
05-29-2016, 12:33 PM
#6
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I'll have to do this tomorrow. I downloaded the build sheet like Rednroll suggested above but I don't 100% trust it because it also says I have a 22.5 gallon fuel tank and I know for sure that that ain't true. Thanks!
05-29-2016, 01:13 PM
#7
Super Moderator
The tank is a 22.5 gallon tank. If you read the manual you will find there is typically 2.8 gallons left once your low fuel light chimes on. If you're saying you know for sure, that it isn't a 22.5 gallon tank then that means you ran it until you were empty and then filled up right after you ran out of gas?
Last edited by Rednroll; 05-29-2016 at 01:23 PM.
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05-29-2016, 07:20 PM
#8
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It's always best to double check as suggested. What did the build sheet say your gears were? The tank is a 22.5 gallon tank. If you read the manual you will find there is typically 2.8 gallons left once your low fuel light chimes on. If you're saying you know for sure, that it isn't a 22.5 gallon tank then that means you ran it until you were empty and then filled up right after you ran out of gas?
05-29-2016, 07:29 PM
#9
Super Moderator
The only tank size I'm aware of for the JK is the 22.5 gallon. I usually hit 18-20 gallons when filling up which is on par with the manual. Search and you will find this discussion comes up quite a bit questioning the 22.5 Gal
05-29-2016, 07:46 PM
#10
Super Moderator
The 2dr has the smaller 18.5 tank and the 4dr has the 22.5 tank.
Nobody can convince you that the sheet is correct until you run it dead empty. I have run mine to the point of no return and it still had a couple gallons in the bottom. It's probably compensation for the terrible sending units they had in the TJ's.
Nobody can convince you that the sheet is correct until you run it dead empty. I have run mine to the point of no return and it still had a couple gallons in the bottom. It's probably compensation for the terrible sending units they had in the TJ's.