Recal of Speedo Necessary??

[FPoitra]

Today I splurged and ordered the 315's BFG AT. Got for $140/ea, not the cheapest, but did it anyway. Now heres the questions; Do I really need to relcalibrate the speedo? I did a search and am finding it will be off by 5 or 6 mph. If I dont', will it affect the transmission shifting points? Also knowing that I will need fender flares, those of you with them paired up with the 315's, are the Xenons wide enough to prevent side splatter, or should I go with the wider bushwacker? Oh ya, I got the high idle TSB and it works perfectly, first time dealer ever heard of it. I had to show him a copy of the TSB I got here from TDR. All of the techs were amazed that it worked because they showed everone in the shop. I told him that being a member of TDR is invaluable for advice and information relating to our trucks. He also owns a Cummins and is now becoming a member, but I get his leather jacket if he wins, HA HA. Anyway,info on the recal of the speedo and fender flare protection would be appreciated. Thanks in advance. Freddy



PS: Anyone sell TDR full windshield decals?

 

[XcumminsX]

your speedio is of by 9%. If you can live with it then ok...



Nick

 

[Tejasdge]

I believe that there are other factors to consider than just the speedo being off. When I first got my truck 23,000 miles ago, I had the dealer put on the 315's and recalibrate the speedo. At that time (a year ago), the closest they could get to the 315's 601 revolutions per mile was 636 RP Mile. That left me going 5% faster than the speedo showed. While I gained over 1000 miles on my warranty, I think that it negatively affected the operation of my anti-lock brakes. Now fast forward to last week where I took my truck in for assorted TSB's, recalls and warranty stuff. I asked them to redo the speedo calibration since we now know that it can be done to 601 RP mile. They messed up the flash and put me back to stock tire size(~10% off) and the truck was a dog and shifted differently. Went in today and had to explain to them that they had to go to the other tire size screen on the DRB and input 601. Truck now feels very different. Much smoother on the shifts and the power is back. I'm wondering if my mileage will go up from this change and will be monitoring it. Overhead already shows increase greater than the 5% change. We'll see how the ABS does on the next panic stop.

 

[XcumminsX]

Thanks Tejas... I do notice the truck shifts odd at times. . Bet its because i havent had mine recalo'ed... Since i plan on changing the tires alot from 33-37" tires. . Does anyone know where i could get the TRUSPEED from superlift (i think)



Thanks



Nick

 

[Tejasdge]

I briefly looked at the recalibration modules, but started thinking about all the systems that the warranty could be voided on, and decided to pass at that time until I was out of warranty. He!!, they could void the entire vehicle warranty since the odometer had been tampered with.

 

[KevinO]

As far as a percentage your speedo is off it depends on how fast you are going the faster you go the more your speedo is off. I had 37's on my last truck and drove to daytona beach and back with a GPS on the entire time the truck didn't see two hundred of those miles.

 

[thejeepdude]

Originally posted by KevinO

As far as a percentage your speedo is off it depends on how fast you are going the faster you go the more your speedo is off.

Wrong and right... the percentage is the same, never changes... except over time as your tire diameter changes slightly from wear. The actual # of MPH you're off does change with speed, but percentage stays the same. IE: 10% off means 3mph off at 30mph and 10mph off at 100mph.