Speedo help

[CARHAULIN]

Tires were changed from
stock 16" to a 17"
speedo is 10mph off how do i fix that
stock tires 245 50 16
new 315 35 17

[Benner]

10mph off at what speed? Your speedo shouldn't be off by more than 1 to 2 mph at 60mph between the 2 tire sizes. They have less than .05 inches difference in overall height so basically the same circumference. Chances are you speedometer was off before you changed tire sizes.

[0rion]

yep, the tire calculator says if your speedo says 65mph you're actually going 65.09mph so less than 1mph difference between those 2 sizes.

You can fix your speedo by getting a tune or with a handheld tuner. What makes you think it's 10mph off?

[CARHAULIN]

Speedo off all speeds
dont know if factory gears were changed

[Benner]

take it to a gm dealership and have them check it and fix it. Simplest way to take care of that.

[CARHAULIN]

I feel its off because i fly by like
every one is sitting still
plus ive followed a few semis i know are govened speed at 62
and my speed reads 52

[CARHAULIN]

Gm dealer told me to buy a
vss buffer ..
Would a tranny shop be able to help??

[ls1camino]

I feel its off because i fly by like
every one is sitting still
plus ive followed a few semis i know are govened speed at 62
and my speed reads 52

Um...no they're not...I've been with a few semis that are going 70-75mph

[CARHAULIN]

All day every day im out there
i know what companys are and which
are not. But thank for a reply.
Stopped at tranny shop tonight they
said something about a drac modgule being bad
and to go the dealer??

[0rion]

let us know how it works out for you

[GatorSS]

It is simple to correct with tuning software or even a handheld tuner. But first, you need to know what the rear end gear is.

[CARHAULIN]

Thanks that seems to be my best option