dennisafrompa

The wheels pictured are not those that came standard of the Shelby GT. Standard wheels were 18" Bullitt style with black spokes. So your wheel tire combo could throw off the speedo. Seems strange to change the intake from stock Shelby GT. That along with GTA mufflers were a few of the standard changes from a normal '07 GT, along with the 3:55 rear.

TheDivaDanielle

what's the tire size? they look massive.

Newell77

Ok.. so rear tires are 285/40 zr18 and front tires are 255/45 zr 18.

You guys have all been super helpful, but my head is spinning. This car is like a gigantic mystery.

dlazrael

40r18 should be close to stock shouldn't it? not enough to throw off as much as he's saying... I agree with the others, it SOUNDS like gearing, maybe......

Welcome to MF.. There's tons of things to learn here, lots of how-to's and all sorts of people to help out

Newell77

Ok..so did some more digging and found this about my car. Although it looks like rims may have been changed since. Again remembering I am an idiot, what mods did he make from "stock". 1st pick before I purchased, second pick when purchased.

2007 Shelby GT #278
Black 5 Spd
Shelby Gunmetal Razors 18"
18"x9" Front
18"x10" Rear
Continental Extreme Contact DW Tires
255/45/18 Front
285/40/18 Rear
Baer Slotted/Drilled Brakes
Hawk HPS Pads
Goodridge SS Brake Lines
Shelby Caliper Covers
Shelby "Berg" faux gas cap
Polished lower Billet Grille
Sequential tail lights
Carroll Shelby autograph
Black Billett Shelby hood locks
Clear front bumper lights
CDC Gt500 dead pedal
8" antenna
Dark tint windows
KR500 axel backs
Steeda UD Pullies
Ford 4.10 gears

drewsky

That's exactly what I assumed about the gears.. Your speedo is set at a 3:55 ratio. So not only is it off but your also putting a lot of extra miles on the odometer that your not driving. What's weird is the stock GT air box, the one in the trunk is the one that comes with the Shelby GT's. Call Brenspeed or American muscle and have them write you a tune and send you a hand held tuner, then install the cold air intake in the trunk. I don't think the bigger tires will effect the speedo much at all after you change it back to 4:10 (maybe 1-2 mph at high speed, no biggie) kinda curious why the stock air box is there and the axel backs? makes no sense to me. However the other upgrades are quality parts and a plus!! Brakes and such are pricey.

americaniron

The open air element intake is your stock one for the Shelby GT. It should be a Ford Racing one

https://www.google.com/search?q=stoc...ml%3B400%3B364

You should also get up on this web site for more specific info on your car from these guys.

http://www.teamshelby.com/forums/ind...-shelby-forum/

wcgman

Call americanmuscle with the list of mods as well as your VIN number and order a new tuner. You will want to reinstall that Ford Racing CAI that's in the the trunk as well. Your car will probably feel like it performs better after you have the new tune installed. Sounds like whoever put this car together did a decent job. Those are some good modifications. Where did you get this list of mods that were installed? If the dealer contacted the old owner for that list, perhaps you can ask them to relay your information to the previous owner so you can contact them and ask if they still have the tuner. You can offer to purchase from them assuming it's still paired to your car.

Newell77

So I installed the CAI and figured out the mystery, but I was wondering.

If I am not planning on doing a lot of mods or racing should I spring for a handheld tuner or take it to a shop and get the speedo corrected?

SPARTAN VI

Without knowing what tune is currently on there, I'm not certain putting the CAI on there is going to help at all. Either way, you'll want to get it tuned with all the add-ons listed out. A custom dyno tune will run around the same price as a handheld tuner ($500ish). I'd go with the handheld tuner with a canned tune from American Muscle. You can make your own adjustments with it too, which is particularly helpful if you ever find yourself changing your tire size.