Speedometer Issue?

[Tim99GT]

So as some of you know i recently installed the roush performance series gauges. Well i noticed that my speed is a hair off. I am about 5 MPH too fast. So yesterday i took and reflashed the computer( I have 3.90 gears by the way) Thinking that maybe the computer had reset or something when i did the install. Still doesnt feel right.


Anybody have any comments as to why my speedo is still off?

[mustangdaveg]

I use a Dallas Mustangs Speed Cal....mostly because I change wheel/tire sizes from track use to street use...also i had a different gear set at one time. Pretty happy with the Speed Cal....when I compare my Speedo to my GPS I'm 3-4 mph faster on my speedo...I can live with that

[Tim99GT]

Well i have the SCT Livewire, and before i had the new gauges everything was fine.(AS far as being flashed with the new gears)

When you flash a comp does it reprogram the speedo cluster chip also?
Reason for me asking is when i swapped the gauges i never flashed the car back to stock. Then when hurrican Gustav hit i had to go back to 87 oct because everyone was out of 93. would this somehow affect it? if so would it help to install the old gauges, then flash to stock. Then install the new gauges again and retune?

[mustangdaveg]

sounds like a lot of work....for a 4-5mph glitch...but what do I know...I pretty much go by what my GPS is reading when I'm out cruising the interstate at 70+

[Tim99GT]

Well i guess its no big deal. Just like it to be right.
Thanks anyway!

[mustangdaveg]

the stock gauges "supposedly" have a 3-5mph error from the factory...at least you don't get a digital read out the says...SLOW...BETTER...FAST....FREEWAY...RACE...SUB-LIGHT...and...WARP Factor 5 Mr Sulu if you please.

[Tim99GT]

LOL!! True!

[roushstage2]

I have a 5 MPH faster gauge too. I changed the tire RPMs to be closer to the actual, but it doesn't seem to be correct still??? Whatever.