Ok so I need a good explanation, I am having problems with my speedometer being off by as much as 15 mph at 60mph. Only gets worse as speed increases. Everyone keeps telling me that my tire size is off and the stock size for my 05 3500 srw is LT245/75R16. I believe and was told my truck is stock. It has LT265/75R16 on it. Attached is a picture of the sticker inside my door. It clearly says 265. Also I remember reading somewhere that GM 1-ton SRW definitely came factory equipped with 265's. Also, it is not the stepper motor problem. Already had that fixed. Is it a speed sensor? Is this rare for this truck to come with the 265's? What am I missing here?
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