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Old 01-01-2013, 06:50 PM   #1
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2012 and newer...

In an auto trans. with larger tires, at what rpm does your Jeep shift to 2nd under moderate acceleration?

I have 33's, didn't re-program...sometimes I notice a 3k rpm shift.

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Old 01-01-2013, 06:58 PM   #2
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I have 4.10s in my Rubicon. 3k rpm shifts into 2nd is pretty normal in mine.
Our 2012 Grand Cherokee Limited with the Pentastar and 3.09 gears shifts close to 3k rpm too.

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Old 01-01-2013, 07:49 PM   #3
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Oh ok... Just seems a little high for light to moderate acceleration.
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Old 01-01-2013, 08:12 PM   #4
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Light acceleration mine shifts to 2nd at 2000. Moderate acceleration it'll shift to 2nd at 2500.

This is probably influenced by the self-programming learning module which adapts to your driving style during the first 50 warm up cycles. If you beat on it, it will let the revs build higher before upshifting.
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Old 01-01-2013, 08:21 PM   #5
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Quote:
Originally Posted by MikeK46 View Post
Light acceleration mine shifts to 2nd at 2000. Moderate acceleration it'll shift to 2nd at 2500.

This is probably influenced by the self-programming learning module which adapts to your driving style during the first 50 warm up cycles. If you beat on it, it will let the revs build higher before upshifting.
I have 4400 miles... I've been fairly easy on it. It must be something I just noticed, and I'm sure the 33's don't help matters...
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Old 01-02-2013, 01:11 AM   #6
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It should shift at the same RPM provided you're giving the same amount of throttle.

33's are almost the same height as the OEM tires, but even so I'm not sure what the tire size has to do with consistent gear changes.
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Old 01-02-2013, 09:59 AM   #7
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It should shift at the same RPM provided you're giving the same amount of throttle.

33's are almost the same height as the OEM tires, but even so I'm not sure what the tire size has to do with consistent gear changes.

I wonder if the shift points are tied it with the speedo indicated speed and if that is the case if you have larger tires your computer will get confused because unless you calibrate your speedo the taller tires will throw it off. If the tires are true 33's they can be almost 2" taller then stock 32" tires from reports I have read some people have measured them closer to 31".
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Old 01-02-2013, 10:32 AM   #8
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Quote:
Originally Posted by The_Chief View Post
In an auto trans. with larger tires, at what rpm does your Jeep shift to 2nd under moderate acceleration?

I have 33's, didn't re-program...sometimes I notice a 3k rpm shift.
I had the same issue, once u reprogram its all good.
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Old 01-02-2013, 12:25 PM   #9
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I wonder if the shift points are tied it with the speedo indicated speed and if that is the case if you have larger tires your computer will get confused because unless you calibrate your speedo the taller tires will throw it off. If the tires are true 33's they can be almost 2" taller then stock 32" tires from reports I have read some people have measured them closer to 31".
The OEM tires are slightly taller than 32" and most "33's" are a few tenths under 33". The difference is almost non-existent, a few revolutions per mile.

The transmission determines when to shift based on many factors, including engine speed, throttle position, engine intake vacuum (a function of throttle position and engine load), road speed, and trans. temperature.

The unsprung weight of the tires will have a much greater impact than a few tenths of height. There will be more load on the motor, having to deal with the additional resistance of the extra weight. This means that at the same throttle position as before, intake vacuum will last longer and the motor will therefore rev higher before upshifting. Is this perhaps what you're referring to?

But like I mentioned, it's also adaptive and will learn your driving style over the first 50 warm up cycles. If you have a lead foot, yours will hold the revs longer than mine. If you're inconsistent (light foot some days, heavy foot other days) that's when you might find issue with it. They assume the same person driving the vehicle consistently.

Try resetting the ECU to clear the learning module and then drive it like you normally would to re-program it with your new tires.
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Old 01-02-2013, 12:31 PM   #10
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The OEM tires are slightly taller than 32" and most "33's" are a few tenths under 33". The difference is almost non-existent, a few revolutions per mile, and won't be enough for you to notice any difference in shift points.

The transmission determines when to shift based on many factors, including engine speed, throttle position, engine intake vacuum (a function of throttle position and engine load), road speed, and trans. temperature.

But like I mentioned, it's also adaptive and will learn your driving style over the first 50 warm up cycles. If you have a lead foot, yours will hold the revs longer than mine. If you're inconsistent (light foot some days, heavy foot other days) that's when you might find issue with it. They assume the same person driving the vehicle consistently.
I know on my 2013 the stock tires were around 29" actually measured.
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Old 01-02-2013, 12:42 PM   #11
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I know on my 2013 the stock tires were around 29" actually measured.
I guess I should've mentioned that I was referring to the 18" wheel/tire package.
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Old 01-02-2013, 12:52 PM   #12
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I guess I should've mentioned that I was referring to the 18" wheel/tire package.
hard to keep every thing straight lol. in the other post he says 34" tires so many choices lol. I agree with what you are saying with all the varibles involved.
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Old 01-02-2013, 02:58 PM   #13
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Originally Posted by MikeK46 View Post

The OEM tires are slightly taller than 32" and most "33's" are a few tenths under 33". The difference is almost non-existent, a few revolutions per mile.

The transmission determines when to shift based on many factors, including engine speed, throttle position, engine intake vacuum (a function of throttle position and engine load), road speed, and trans. temperature.

The unsprung weight of the tires will have a much greater impact than a few tenths of height. There will be more load on the motor, having to deal with the additional resistance of the extra weight. This means that at the same throttle position as before, intake vacuum will last longer and the motor will therefore rev higher before upshifting. Is this perhaps what you're referring to?

But like I mentioned, it's also adaptive and will learn your driving style over the first 50 warm up cycles. If you have a lead foot, yours will hold the revs longer than mine. If you're inconsistent (light foot some days, heavy foot other days) that's when you might find issue with it. They assume the same person driving the vehicle consistently.

Try resetting the ECU to clear the learning module and then drive it like you normally would to re-program it with your new tires.
Ok cool...makes sense. So what do you feel is a general low end / high end range for rpm's coming out of 1st, not babying it or flooring it?
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Old 01-02-2013, 04:49 PM   #14
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2500-3000.
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Old 01-02-2013, 04:59 PM   #15
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2500-3000.
ditto
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Old 01-02-2013, 11:24 PM   #16
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My daily commute is three trips totaling 15 miles, sometimes less. I have days where I never exceed 2000RPM, when there are no cars on the road and I just want to enjoy driving my Jeep. I'm so light on the throttle it's upshifting at the earliest point possible, which is 2000RPM. Sometimes the fuel gauge never moves the entire round trip commute.

Sometimes I take the long way home for no other reason other than to extend the drive. Weekends are the only time I get out and explore the world. Still, I got my JK nine months ago and I just cracked 4500 miles today. I'm averaging less than 18 miles per day. Since my mileage is so low I have to extend the time I spend in my Jeep other ways

I guess what I'm trying to say is, the lightest possible throttle application results in 2000RPM shifts.

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