The dealership had my truck for a few repairs and I asked the manager about reprogramming the speedo for my new tires (315's). No problem I'll do it for free. He programmed it for 601 revs per mile now it runs 13 mph faster than the true speed. So 50 mph = 63 indicated What gives? I know some of you guys have had this done.

 

According to the BFG website 601 is correct for their 315/70 tire so it should be close. Sounds like he may have made a little typo. I just took mine in yesterday and offered the revs/mile that BFG gives for the tire I have but the dealer said they did not need that number they have their own formula they enter. I haven't checked it yet but I think I will this afternoon.

 

I had the same problem. You'll just have to go back and get them to re-do it. Just tell them you had it done the other day and it's not right. The 601 Revs is the right number and it will turn out OK. I don't know why that happens.
When the dealer did mine the truck was running and he just yanked the plug out in a hurry when he was done. Sure enough it was way off, so I went back.

Wetspirit

 

What could be more correct than the BFG number that everyone else is using and has been proven to be right???????? Sheesh. The dealer has to enter a number, why can't he use the one you already have? That might be too simple.


Wetspirit

 

Had my dealer do that for me and it's accurate. Take it back and have them redo it.

 

I checked my speedo before and after the re-calibration with my GPS: before the re-cal, my speedo read 5-6 mph slower, after the re-cal, the speedo was spot on. I also told the dealer 601. However, they charged me $80, at least yours was free

 

Had mine done to accomodate 37 inch tires and gps tells me its within 1/2 mile per hour. Good enough for me.

 

Took back the truck to have the speedo checked and it was set to 601 as he said I verified it. So I just had it set back to stock. It was nice to be able to run a hundred mph and get 24 miles to the gallon.

 

You just extended your warranty by about 10%. You now have a 77,000 mile powertrain warranty and 110,000 mile Cummins warranty.

 

shakey 601 is the correct number i just did mine while i was at work the other day and by the gps it is right on the money. they must have done something wrong. tell them to use the original tone ring setting and just change the revs to 601 and it should be right on. i garuantee he accidently changed the tone ring setting . if you have any questions i can plug the drbIII back on my truck and tell you exactly what it says and you can tell your dealer how it is done
d12

 

I do appreciate it. It's really not an big issue with me. As a side note when he reprgrammed it back for the stock tires the change was not correct either, it took two times to get it correct for the stock setting. Maybe you could PM me the proper procedure so the next time I go I'll have it. Thanks.