6.0 speedo a POS?

[redbandit98]

Yes, I know I have the same thread in the electronics section, but I think it would be better suited here. I finally got my autoenginuity kit to adjust my speedo. I ended up having to go with a 31.5 " tire size to get my speedo to read correctly with 34.5" tires. What gives? Are the speed sensors just that far off?

[redbandit98]

nobody? I played around with it. A 31" tire puts the speedo dead on with my GPS. The tire is a 275/65/20..There is no way you should have to put a tire thats 3" less in diameter to get the right speed?

[WBFD47]

Same size tires on my 06 although they are worn and will be replaced in a couple of months and my Speedo agrees with my GPS.

Chuck

Sent from my AT100 using AutoGuide.Com Free App

[WarChild]

Mine is dead on with gps.

[ZMANN]

I put in the measured size of my tires via A/E not the mfg rated size and it was dead nuts on with GPS

the speedo sensor reads a ring in the rear dif it's not likley to misread

[Dave]

When using AE always go with the measured size when they are on the truck.

[redbandit98]

ill go measure them. I doubt they are a full 3.5" smaller than theyre supposed to be but who knows?

[redbandit98]

Im bringing this back up becuase its really annoying me. I put my tire diameter back to 34" which is what they actually are. My speedo is about 6-7 mph off at 60 mph. I went ahead and verified that I do, in fact, I have a 3.73 ratio. (bought the truck used). Verified it was a 3.73 (marked the driveshaft counted the turns vs tire etc). I can go out on the interstate and use the mile markers and with the tire size being 34" and the speedo reading 6mph fast, the odo is off by about two tenths. In other words I show IVe gone a mile two tenths before I actually hit the mile marker. Im not so much worried about the odo, but the speed being off that far is p#@#ing me off. I dont mind leaving the 31" tire setting in there as long as Im not messing with the shift points etc. I think Im just gonna split the difference and have it ~3mph off and say it has a 32.5" tire. Ive looked under the hood for a speed correction device or something but havent found anything. I just cant imagine it being that far off from factory. Door sticker says it came with 265/70s.

[ZMANN]

rear end ratio doesn't mess with the speedo just tire size ,, why you ask? the sensor picks up a signal after the ring gear in the differential so it is not effected by changes up stream

IDK now why yours is being a problem???
but most speed correction devices are under the dash