I think I'm with Red Rock on this one. If the speed sensors are taking their readings at the wheel, the gears have nothing to do with it. If the speedometer is taking it's readings from the drive shaft, then it would. I believe the JK gets its readings at the wheels, based on other threads I've read.

When I pedal my mountain bike, the speedometer doesn't give a rats ass which of the three front derailers I am using, because my sensor is on the wheel. That just determines how hard I have to work to keep it at a certain speed.

In order for the gears to make a difference, the speed sensor would have to be reading the driveshaft.

 

Yes I have this setup. I used a GPS to check my speeds when I had 35's and 4.10 gears. I checked my speeds with 35's and 5.13 gears, and my speedo is off by the same amount as it was with 4.10's. Evidently the JK gets it's speed readings by the rotation of the tires (IE wheel sensors.) That would make a gear change make no difference in the speedo reading, which is exactly what I have observed. Take it for what you want, but that's my experience with it.

I like Rubimon's analogy. A 20 speed mountain bike with a speedo could care less what gear you are using, it is deriving the speed from the rotaion of the tires. Same concept applies here. You can write my post off as anecdotal evidence if you wish, I'm just posting my experience with it.

FWIW, I was totally expecting my gear change to affect my speedo a lot. I have an extensive background in vehicle repair, customizing, etc. and I know that is the normal thing that happens when you swap gears. When I got my 5.13's installed and it did not change my speedo readings I was very surprised. That lead me to the conclusion that the speedo reading is based off the tire rotation (read by the wheel speed sensors) and not readings from the transmission, transfer case, etc.

Just my .02 , hope it is worth that to someone.
.
.
.

 

Never writing off anyone's post... all information is valueable... In fact, as I mentioned earlier... being that you have the exact setup I'm having put on this week... I'm thinking your experience is probably the most valid in order to answer my original question.

Thanks RedRock, I appreciate your time. Also, your part of the reason I went w/5.13's over 4.88's anyway... I read your earlier posts and results in regards to doing this to your JK...

 

 

lol sorry, that comment wasn't really aimed at you. And you are welcome, glad to share my experience!

 

That is an awesome offer !! THANKS !! Is there a software, hardware, or program device that can be purchased to do these functions?

 

What a great offer..... ...You think my wife would buy the fact that I needed to get my speedo adjusted for free and while I was there they accidently put a hemi in there for me!

 

No, just tell her that they recalibrated your speedo for "X" thousands of dollars and then tell her they threw in the Hemi for FREE!

 

Dan, do any of us out of towners have another option? I'm in AZ. Would a device like the Scangauge II allow me to enter codes to do this or only read them from the OBD2 connector? Thanks.

 

All hemi installs get a free speedo calibration. I know of no other way to do it . So come on by---
Dan