Hey Guys,

Putting 325/70R17 Nitto Terra Grapplers on my '08 2500 6.7L tomorrow. I went by my dealer today and was told by them that they cannot reflash the computer to adjust for ANY tire or gear sizes on the 07.5 and 08's like they could for the 5.9L's. I am sure I am not the only person in the world who has put larger tires on a 6.7L so I am wondering how you guys are getting your speedometer accurate. I am concerned with an accurate speedometer but also an accurate odometer so getting something like the Edge w/Attitude won't help me. Granted it will show me the correct speed, but my odometer will still be turning slower than it should be. Any and all imput would be greatly appreciated.

-Bud

 

my power pup adjusts the speedo, up above 37's.....i didnt try to go further since thats all i needed

 

My Dealer did it on my 08, 265 to 285, Just tell Love's Dodge to do it.

 

Did you have it done at Loves, DODGE4X4? I asked Cantwell in Kingsville today and they said they can't do it on the 08's. Blowing smoke perhaps?

 

Tire size is adjusted via the TIPM.

Need to know circumference in mm instead of revs/mile.

I'd tell them you're not coming back cause they are not honest.

 

My dealer, in Charleston, WV said they don't have anything to do the 07.5's and 08's yet. They can do 07 and back with no problem for what ever size you want.

 

That's what Cantwell/Quality told me yesterday. I am going to just stop by Love's Dodge here in Alice today after I get back from Corpus with my new tires on and see what they say. Hopefully they can do it, that would be great!

Based on my calculations, since I have 3.42 gears and will be going with a 325/70R17 tire, i should need to recalibrate the computer for 3.73 gears and 275/70R17 tires. That should get me pretty darn close. Can anyone confirm my calculations are correct?

 

06 and up do not adjust the same as 03-05. It's not by circumference. The dealer can adjust to each of the tire sizes that are available from the factory only, with the StarScan tool. The largest is the 285's that come on the Power Wagons. Look at DODGE4X4's post. He's absolutely correct.

 

Can the StarScan tool also do gear ratio changes between factory options? Going to a 285 programming won't get my speedometer much closer than the 265 programming is, but I have 3.42 gears in the truck and programming it to think there are 3.73 gears would get me awfully close (<1 mph off at 70mph).

 

Good question... I see where you're going with it. But I do not know the answer. My experience is watching them use the tool on my truck twice. The Tech was actully willing to answer questions about what's available and how it works...
Superchips make a tool called the Tire Paq that will program like the old 03-05 guys are used to (tire circumference). But the 6.7L version isn't out yet. Also, I've talked to two Speedometer Calibration places in my area that say they can program larger tires than the dealer can. They both will run it on a dyno to confirm the settings. They both were $99.

Also, I think the issue is not that the computer doesn't understand the circumference settings any more but that the StarScan tool doesn't offer that in the menu's anymore. It's a drop down menu that only offers preprogrammed selection. This is probably why the aftermarket programmers can.

 

Well I took my truck to Love Dodge here in Alice and the service tech said he could do it up to 315's. I told him I thought 285 was the highest he could go but he said he could do it so i told him "close enough for me" and left him the keys. About an hour later he called and said that his software wasn't updated for the '08s so he couldn't do anything. I had forgot to ask them where they were getting ULSD in town so I called back later and they said they had done some more looking after I left and it turns out that they wouldn't be able to go over a 285 and that wouldn't help me much. I asked him if he could do a gear change and, after looking up in his own calculator to verify that programming for a 3.73 diff gear while having a 3.42 actual diff gear in the truck would make the speedometer under 1mph off at 70mph, he said he could. So, I am going back early tomorrow afternoon and hopefully they will be able to get the gearing change plugged in. If so, I will be VERY happy. With only 1700 miles on the truck, anything I get done right now I would rather have done at the dealer. I don't have any plans for any programmers other than a Quadzilla MMM when they come out for the 6.7L so if the dealer can get my speedometer reading right I will be as happy as can be. I will let you guys know tomorrow how things go. Thanks very much for the imput thus far.

 

Wow, very interesting info. I am curious to hear how it turns out. Do you have a GPS unit to verify how close they actually get?

Also, (gonna show my ignorance now) is there any chance by changing the gear ratio, it will effect the shift points in any negative way?

 

I won't be able to comment on the shift points as I have a 6-Speed Manual but as far as the confirmation is concerned, I don't have a GPS so I had to do a little creative planning. I paced my '01 with my '08 before I put the tires on to confirm that 70mph on the '08 was 70 mph on the '01. They were spot on with each other. Now, I will have to pace again once they adjust the settings and use the '01 as the control group this time. That should tell me (roughly, i realize this is about as flawed a scientific experiment as can be but I am not looking for accuracy within 100th of a MPH) how close they got with the new truck. My buddy has a Garmin but I am not sure if it is GPS capable. If it is, I am going to use it as a secondary confirmation source.

As far as the shift points are concerned, I would think they would be relatively unaffected. Correct me if I am wrong, but aren't shift points based on throttle % and engine RPM? If so, the shift points should remain unchanged.

 

I went back to my dealer 3 times trying to get my trucks speedo dialed in. I'm still off by 4mph at 60.

I officially gave up.

 

Im a bit confused.....so your truck has 3.42's, ok got that, and you are putting 325's which are taller Ok then you are going the wrong way by tricking the computer into thinking you have 3.73's. See with taller tires you will now be traveling at a higher speed per revolution, yet the computer will now think you are going slower cause of the new 3.73 programming. RPM vs RPM a 3.42 will be going faster If you had 3.73's then telling the truck it ahs 3.42's would be a step in the right direction