Question on Resetting Shift Points

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Cainer

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Recently lifted my 2014 (obligatory pic below) and added 35" tires. After driving it a bit, I've noticed that the (8 speed) transmission shifts kinda wonky now. Like it revs high for a lot longer in first than it ever did. Is this something unavoidable due to the excess weight/drag of the bigger tires or does my transmission think it's moving slower than it really is, so leaves it in first longer? Is there any way I can fix this? Will disconnecting the battery for a while make it forget the old shift points and learn new ones, or since it doesn't 'know' it has 35s on there will it just relearn old bad habits like I so often do? :)

IMG_1327.jpeg
 

tnctx02

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I don't remember mine feeling that different after installing the 35s. But the speedometer was way off.
I already had a Hypertech speedometer calibrator and had plugged in the new tire size a few days after getting them installed.
Got the speedo within a 2 mph so I left it there.
I haven't used it, but I beleive you can use AlphaOBD to do the same thing with the speedo. See if that helps with it.
 

ram1500rsm

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Calibrate your speedo for the new tire size and she should start shifting as good as she did stock. Anything that can calibrate the speedo will work, the cheaper option will be Alphaobd but seems to be a little pita given the number of steps.
For example

I use Hptuners and with it is just one click, then it'll ask you for final drive gear ratio which (3.21 or 3.55 or 3.92 or any other gearing you may have) and new tire size (diameter in inches) and that's it.
Most tire size calibrators also work in similar way so adjusting tires/gearing is super easy with such options. Some may ask for tire diameter, others may have for circumference (Pi x Diameter) etc.

The secret is not to use the theoretical size of the tire, like a 35 is not a 35, in my case my tires are supposed to be 34.8" advertised, but if i measure the tire under the truck weight from ground to the tire shoulder edge, i get 33 1/4". In my case any of the 315's i've tried put my odometer spot on with 33.37", i'm a little **** when it comes to this stuff so i take my time with it. :)
Measure your tires from the ground to the should edge of the tire and use that number as yor base for the calculation then test your MPH against your GPS. you may need to adjust the number for the tire size more than once up or down, rinse and repeat until your odometer reads the same as your gps.

50062561391_b92e0c3a0b_3k.jpgPatagoniaMT_Shoulder_315_70_17 by RAM RSM, on Flickr
 
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I used ALFAOBD and it was simple ... I however also did regear which made things much better ...

Try ALFAOBD it's really simple and you can do a lot of other things with it as well ... if you ever need LEDs or HIDs you can have those without extra harnesses or canbus modules ...
 

dylanpresley

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I used ALFAOBD and it was simple ... I however also did regear which made things much better ...

Try ALFAOBD it's really simple and you can do a lot of other things with it as well ... if you ever need LEDs or HIDs you can have those without extra harnesses or canbus modules ...
What does it ask for when you reg eared? And what’s the gear ratio that worked well?
 

CanuckRam1313

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Recently lifted my 2014 (obligatory pic below) and added 35" tires. After driving it a bit, I've noticed that the (8 speed) transmission shifts kinda wonky now. Like it revs high for a lot longer in first than it ever did. Is this something unavoidable due to the excess weight/drag of the bigger tires or does my transmission think it's moving slower than it really is, so leaves it in first longer? Is there any way I can fix this? Will disconnecting the battery for a while make it forget the old shift points and learn new ones, or since it doesn't 'know' it has 35s on there will it just relearn old bad habits like I so often do? :)

View attachment 213707
Are you running 3.21 or 3.92 gears?

This gearing contributes to a huge part of what you're indicating.

I previously had 3.21's on my 19' and the shifting from 1-2, 2-3, 3-4, 4-5 hugely differs from my new 23' with 3.92's on the same shifting.

I also run 35's for my summer set up, but gearing overall contributes a great deal to what you are indicating.
 
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