Steven, Go in and have them change your gear ratio with the star scan... And then go drive it... Have a handheld GPS to know how fast you are actually going.. Just by changing the gear ratio in the computer it got me within 5 MPH .. so when i set my cruise at 75MPH i was doing 80 MPH... i was used to that and then i got it dead on when i bought the powerpup. My tires are 35x12.50R18 Toyo Open Country M/Ts...

 

I have a set of 315-70 R17's, Speedo Reads 60 and the GPS reads 64, just had the lastest trans and engine flash done. Hope my milage comes up after the replacement of a bad O2 sensor

 

Mads Electronics has a new ABS tire adjustments and DTC code reader programmer. You can adjust your speedo.

http://www.madselectronics.com/products.html

At the bottom of the page.

 

How much is that thing? Anyone use one?

 

I don't know the price. It's fairly new product. PM Bob Wagner on here or go on the website and give them a call.

 

They don't have a Smarty out for the 6.7 Liter engine yet.. Its due in November supposedly.. The 2006-2008 Dodges only have a few presets for tires sizes that they deem safe for the truck.. You can only change the speedo to be correct for up to a 33inch tall tire. Anything bigger isnt an option on the computer. You can play with the gear ratios and set the computer to a 33 and get really close to what you want.. i just happened to get it dead on when i used the PowerPup to make it think i have 33"s and my gear ratio i changed to a 4.10 or something with the starscan.. i don't remember exactly

 

I emailed Mads and sent a PM to Bob last week about this Euro IV Modul. No response back from anyone. Maybe this thing is just in the development stage? Strange that no one responds back about this unit.

Euro IV Modul

 

I was able to dial in my speedometer with my new power pup. With 285's, I was running about 2-3 off. It took me 4 tries, but 31.75 was the correct setting and with the gps on 60, the speedo is on 60. I did try to set 32.75, but I was running 5 fast.