Aito Tranny Ratios.

Is there anybody out there that can confirm for me the ratios of the Auto Tranny on a 2007 JK, I just had 4.88s fitted and my RPM and speedo ( pro cal corrected), are the same as my mates, who has a 2011 Auto and he has 4.56s. Both of us have 315x70x17 tyres, diffrent brand ( I know there could be a small difference in the tyre size). Is htere a difference in the 4th gear between the years or are the auto boxes the same 2007to 2011??? My RPMs read 2250 at 110kmh.
Any help would be appreciated.

Did you make sure to measure your tires from the ground to the edge of the shoulder, the corner where the sidewall becomes the tread? Another way to do this is to measure from the center of your wheel to the ground and multiply that by 2. Both methods will give you an accurate measurement and that will give you correct shift points. Now, if you did do this, the only thing I can say is that the programming on the 2011's is the same as the 2012's (even though they use a different motor) and that could be what you're seeing.

wayoflife said:

Did you make sure to measure your tires from the ground to the edge of the shoulder, the corner where the sidewall becomes the tread? Another way to do this is to measure from the center of your wheel to the ground and multiply that by 2. Both methods will give you an accurate measurement and that will give you correct shift points. Now, if you did do this, the only thing I can say is that the programming on the 2011's is the same as the 2012's (even though they use a different motor) and that could be what you're seeing.

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Thanks Eddie, we did not concider that. I guess I was hoping for the RPMs to be at about 2400 to 2500 at 100kmh. I did measure the tyre from the ground to the outer edge of the tyre where the tread starts, and I even used a tape measure with inches on it instead of millimeters (just to make sure I got it right) I just thaught there would have been a bigger difference between the 4.56s and the 4.88s. I have to admit the km/l has dropped to near standard, and with petrol the price it is over here thats a good thing. And by the way we are paying around the $1.50 to 1.56 per litre at the moment.