Rear axel ratio?

[Chris412]

Hi guys, new here so thanks in advance for the help.
So I put my car on a lift last night just to have a look around and saw a sticker on the rear axel that read 3.31. Now I thought all the 5.0's with a standard transmission came with 3.73:1 gears. Do I have 3.31:1?

 

[cbass]

If you bought it new and haven't touched it, it has 3.31's
No telling what kind of life it had if you bought it used, though. I know my old car has the stock housing, and probably a 3.31 sticker, with 3.73 gears.

 

[tjm73]

3.73 gears were always an option if they were available for a given combo.

 

[Chris412]

No I bought it used. Guess I'll just have to pull the cover and count the gear teeth.

 

[oldVOR]

No reason to pull the cover, just jack up the rear and count the number of revolutions the driveshaft makes for one revolution of the tire.
If it goes a touch past 3-1/4 turns, it's 3.31
If it goes almost 3-3/4 turns, it's 3.73

 

[cbass]

Or just drive it.
I made this file to look at speed vs gear ratio while considering options for my old car.
https://drive.google.com/open?id=0BzsCcQ7N5imvbXF1d3NlRm53RWc

 

[oldVOR]

That would work too, however, you'd have to assume the correct ratio is present in the tune for speedometer accuracy. Otherwise, it's guess-work at best.

 

[redfirepearlgt]

Hi guys, new here so thanks in advance for the help.
So I put my car on a lift last night just to have a look around and saw a sticker on the rear axel that read 3.31. Now I thought all the 5.0's with a standard transmission came with 3.73:1 gears. Do I have 3.31:1?

2011+ Coyote 5.0's come standard with 3.31 gear for the 6 speed manual. 3.55 and 3.73 are the other two options.

As stated there is no reason to crack the rear cover. jack the thing up in the back, mark the DS on the side you wish to rotate your tire, mark the tire, and with the car properly chalked up front and the car in neutral, rotate the rear tire one turn while counting the DS rotations. AS said if it goes a little past 3 its a 3.31, if the marks makes it almost all the way back around on the DS for a fourth turn its a 3.73. Anything above a 3.73 is aftermarket.

 

[tjm73]

Got a GPS speedo app on your phone? Go out and run it at a steady 2000 rpm in 5th gear (1:1) and note the speed on your GPS app. With stock size tires (27" +/-) it should be 48 mph for 3.31's, 45 mph for 3.55's and 43 mph for 3.73's.


Formula: (tire height x rpm) / (mph x 336) = gear ratio

 

[46addict]

Another thing you can do is look at the door tag and find the axle code. Look up the code and see what ratio it translates to. You could do this on the 05-09 cars and I'm assuming 2010+ is the same.

 

[pass1over]

Another thing you can do is look at the door tag and find the axle code. Look up the code and see what ratio it translates to. You could do this on the 05-09 cars and I'm assuming 2010+ is the same.

The tag's on the rear-end though as to what ratio it is. As long as it's still the stock ratio.

Mine has a sticker just like that one, but it says 3.73 as I have the 3.73 gear option from the factory.

 

[46addict]

The tag's on the rear-end though as to what ratio it is. As long as it's still the stock ratio.

Yeah that's the catch. I had to re-read the post to see OP posted a picture of his tag.

 

[Chris412]

Thanks guys I did the GPS speed and found a rpm/gear calculator. I do have 3.31. At least now I know what my next upgrade will be.

 

[Grabber Blue 5.0]

Gears aren't necessarily an upgrade. A lot of guys say the 3.73's are way too short.

 

[46addict]

For a 6R80 or a MT82, I can see how they would feel too short. But they are good street gears for a 3650 car and some prefer 4.10s.

 

[cbass]

I was still under 3k in 6th at road trip cruising speeds after the 3.73 swap.