I have an 08 wrangler unlimited, with a 2" lift and 33x12.50x18
(original 255/75/17) and it seems like it back shifts out of overdrive alot? Does anyone know if having the stealership relcalibrate the speedo($100) will help with shift points? or does it just correct the speedo? I am actually only 1-3 mph off at the very most according to GPS so I just don't want to do any damage to the tranny buy not correcting it??
Thanks in advance
Jason
r6realtor

 

I don't think correcting the speedo will do anything for you. The ECU shifts according to engine load and other factors, actual speed doesn't really matter.

 

Recalibrating the speedo will fix the shift points. But from what I understand the dealership can only go up to a 32" tire. Procomp makes a recalibrater for home use.($200) http://project-jk.com/jeep-jk-write-...ter-calibrator Also if you are going to spend to money hypertec makes a programer that will do all of the above and tune your engine for better performance.($400) Hope that helps.

 

$100

I would think that it would not take more than .25 hour of shop time. I would asked another dealer. Otherwise the aftermarket programmers will work. Maybe someone in a local Jeep club has one that you can borrow to make the change.

 

The nominal size of your 255/75/17's are 32.059". Since you went to 33/12.50/18 there is a difference in diameter, however the difference is not that much, perhaps 1/2". On the other hand the tire you now run most likely is heavier, and has more rolling resistance, thus the change you are feeling in the shifting pattern of your x-mission, much like you would feel when increasing your payload or towing.
If your dealer can re-flash to 33", that might be an option, however you don't say what your current gearing is, and that to me is a larger factor than re-calibrating the sppedo and shift points. Since you have an 08, your gears may be 3.21's in which case the gearing is more for gas miliage rather than performance. With that in mind even with a re-flash, you might still feel the x-mission lugging, and therefore downshifting.
Even 3.55 gears seem a bit undersized to me for 33" tires. I would want no less than 4.10's.
Sometimes people see larger tires on Jeeps, and think they look kool, without any forethought as to the ramifacations of installing those larger tires. This also applies to other mods as well, like bumpers, winches, skidplates and the likes. One must remember the stock JK, came from the factory as a unit. That is the vehicle weight, tire size and any factory options as well as the factory gear size were put together to optimize both performance and economics for the vehicle. By adding weight or rolling resistance to the vehicle the performance will change. For this reason you may want to look at your gear size and act accordingly.

 

Amen brother

 

damn 100 dollars to reprogram....dealer here in pa did it free of charge....ofcourse i did have both front ball joints replaced,and tie rod. and 3 clutches,all within the first 12,000 miles maybe they just owed me

 

A third Amen to what Lorrel said.

And then we go hang all this heavy stuff on them. Gears are the answer. 5.13's did wonders for mine.

 

I have 3.73's and I definitely agree about the rolling resistance but I am sure plenty of people are putting a much larger tire on than myself with even less gearing, so it seems some are saying that if I do recalibrate it may help a little??? I may spring for the accupro, can you use it on multiple vehicles? thank you all for your helpful advice!

 

I don't think so. At least the Hypertech is tied to the vehicle by VIN.