Rearend

[Jsidorek]

I have a 2006 S281 it says on the window sticker that it has 3.73. I was cleaning under the cars rear and a sticker on the back plate of the rearend had 3.55 how can I tell

[david01130]

Im pretty sure ford made the stock gts with 3.55s so when Saleen got them they had the stock 3.55s. Mine was never upgraded to the 3.73s so it still has the 3.55s. Yours probably has the 3.73s someone maybe just didnt take the sticker off from the factory. Is it a ford sticker or saleen sticker? Either way you can check by lifting the back end of your car off the ground and rotating the rear tires one revolution and see how many times the driveshaft spins. You can do this by making a pointer to the driveshaft and marking it with chalk. Can be difficult to do but you can tell if it goes either half way around on the third turn (3.55s) or 3/4s around (3.73s)

[islander033]

Originally Posted by Jsidorek

I have a 2006 S281 it says on the window sticker that it has 3.73. I was cleaning under the cars rear and a sticker on the back plate of the rearend had 3.55 how can I tell

Is your car 5 speed or auto?

What is your rear tire size?

What is your RPM in your highest gear at 70mph?

[wpgfordguy]

look for a X373 stamped into the steel of the diff cover ( usually near the bottom of the cover)

[Meikol02]

My car has the same original Factory ford sticker but is supposed to have the 3.73 upgrade as well. I will have to look for the stamp this weekend.

[islander033]

Originally Posted by wpgfordguy

look for a X373 stamped into the steel of the diff cover ( usually near the bottom of the cover)

The stamp is only legit if the car was not modified after the original purchase from the dealer.

[Meikol02]

Is that pre-Saleen or Post Saleen?

[islander033]

Originally Posted by Meikol02

Is that pre-Saleen or Post Saleen?

Post Ford for sure.

I'm not sure if Saleen stamped the diff cover or not.

You might want to see your Saleen window sticker to see if they modified it.

[Meikol02]

The Saleen window sticker on mine and the other guy say it was done, but that is not a guarantee. My car was shipped without the HID headlights noted on the window sticker (rectified thanks to Jess Albright before the drama at Saleen started).

[islander033]

Originally Posted by Meikol02

The Saleen window sticker on mine and the other guy say it was done, but that is not a guarantee. My car was shipped without the HID headlights noted on the window sticker (rectified thanks to Jess Albright before the drama at Saleen started).

Then you can always do this: "Either way you can check by lifting the back end of your car off the ground and rotating the rear tires one revolution and see how many times the driveshaft spins."

or this: "Is your car 5 speed or auto?
What is your rear tire size?
What is your RPM in your highest gear at 70mph?"

And I can tell you what the calculator says.

[Jsidorek]

Thanks for all the help found saleen tag 3.73

[Meikol02]

Well I didn't get under the car, but she runs right at 2000 RPM at 70 mph with 275/40R20 rear tires in fifth gear (manual).

[islander033]

Originally Posted by Meikol02

Well I didn't get under the car, but she runs right at 2000 RPM at 70 mph with 275/40R20 rear tires in fifth gear (manual).

Calculator is showing 3.55 gears with those tires at 70mph.

[Meikol02]

Originally Posted by islander033

Calculator is showing 3.55 gears with those tires at 70mph.

Well that is peculiar. I looked under the car and sure enough there is a 373 stamp in the bottom of the diff cover with yellow paint across it (like the pulley mark) which I am sure is a Saleen marking. Either the calc's are wrong or someone stamped the rearend without changing out the gears.

What to do now?

[islander033]

Originally Posted by Meikol02

Well that is peculiar. I looked under the car and sure enough there is a 373 stamp in the bottom of the diff cover with yellow paint across it (like the pulley mark) which I am sure is a Saleen marking. Either the calc's are wrong or someone stamped the rearend without changing out the gears.

What to do now?

There is not a real big difference between 3.55's and 3.73's.

Try these combinations:

In 3rd gear at 3000 is 52mph with the 3.73's and the 3.55's is 54.5mph.
In 4th gear at 3000 is 68.6mph with the 3.73's and the 3.55's is 72mph.

If none of these match your car, your speedo may be off a bit or your tires are slightly worn.