Need help here. After dealer reset pinion factor, the truck speedometer is now about 15mph too fast. The speedometer is reading 70mph but the tach is only at 1500. My normal 10.5 mile trip one way to work turned into 14 miles this morning and I drove the exact same roads . I still have the stock tires and wheels on the truck until tomorrow when I will be putting 325/60/18's on. I need to go back to the dealer to fix this, but what should I ask them to check? I know for a fact that the RevsPerMile info that the tech put in is correct as I supplied this info to him and he double checked it after he programmed it. I wouldn't think that the mph would change that drastically going from the stock tires 654 RPM's to the new tires 626 RPM's. Should I wait until I install the new tires tomorrow to see if it corrects it? Is there something else the dealer should program?

**I'm now averaging 35.6mpg on the overhead

 

Check with new tires, but get to the dealer ASAP! Essentially, they are cheating you on warranty miles!

 

So you asked to habe your speedo/ pinion factor re done for larger tires and you are still running the stock tires?
Yes then its wrong.
Wait until you have the correct tires that the computer was re flashed for, then see if its accurate.

 

You don't say what you had them set the pinion factor to, stock or the new size. It should be set for the revs per mile of the new tires you'll be installing. Get the revs per mile from the tire manufacturer and have the dealer enter that number. It is possible that a mistake was made when using the DRB tool (that happened to me). I went right back and had them do it again and it ws right. So, just make sure you have the proper number of revs and return to the dealer to get it right. Your new size tire will not be listed in the tool so he will have to choose "other" under tire size, and enter the revs. They should correct the mistake at no charge and even without an appointment because it only takes a minute.


Wetspirit

 

I had the truck in for a state inspection so I figured if they could reset the pinion factor at the same time, it would save me an extra trip back to the dealer two days later when I have the new tires put on. Guess that plan is going to backfire on me

Will driving the truck this way hurt anything or is it just the speedometer that's off?

 

I had the RevsPerMile set for 626, which is the new tire size. I was doing a search here and found something about axle number? 10.5 or 11.5. I'm wondering if that got changed?

 

Your axle is the 11.5. That could be the mistake they made, but I don't know. It won't hurt anything to run around with the wrong pinion factor but it will be shifting at the wrong speed as well as indicating the wrong speed (I didn't notice if you have an auto). I switched to 285s from 315s about 25,000 miles ago and have not reset mine yet. . Smarty soon, then I will do it myself. I've found that most dealers are completely clueless about it or think it's worth about a hundred bux and an appointment to do it . Just go back with the right numbers and get it fixed.

Wetspirit

 

Agree with welndmn.

On a side note, not to derail the thread, but welndmn is that Brentwood NoCal or SoCal? Check my locale.

 

I wish it was socal! (That would mean I was rich!)
I live right off Hwy 4......... Right by the Dodge dealer.

 

Haha...I live at Lake Alhambra, wife works on 2nd in Byron at the County Ag dept. Small world, eh? I couldn't picture a Diesel in Brentwood Socal, but didn't want to exclude it.

If you see a black 06 with Steeler gear on it, it's me...Probably only see it at Winco though, the wife drives the 02 to work.

 

put your new tires on first that should fix it.

 

TonyB, if you will re-read his original post, "they" are not cheating him, he supplied the info for the recalibration. It would seem that yfz431 got what he requested, just not what he wanted.

 

Well. Had the new tires and wheels installed. The speedo is still way too fast, by at least 10mph. Guess I'll head back to the dealer. Something was programmed wrong. Hopefully we can figure it out or at least reset it back to stock. Hindsight - should have left the darn thing alone

 

Where did you get the Revs per mile number that you told them to falsh it too?
That wrong from the sounds of it.
Have them figure it out, there is a forumla for it

 

I had to bring my truck in a 2nd time for the same problem. The first "tech" changed the ring tooth # you dont need to. The 2nd tech actually put the truck on the lift measured the circumference of the tire divided it into a mile to get the rpm of the tire needless to say that # is different than what the tire manufacturer rated the rpm. And I was right with the 2nd tech and if done properly you shouldnt get to the ring tooth # option.