Okay, I'm starting to wonder if I know for sure what my axle ratio is in my 85 2wd f150 with a c6 tranny (which I'm told has a 1:1 ratio in top gear). The door jam sticker gives me a code of: 14 for the axle.

A while back, Steve83 ID'd it for me to be a:

Ford 9" 3.00 ratio, 3550lb. GAWR.

In another thread I was reading and come to find that the 3.00 is a higher gear. Going 55mph down the highway I run about 2100rpms; 60mph(which is the speed limit on state hwy's here) 2200-2300rmps. I've been thinking, at those speeds shouldn't my rpm's be lower with a 3.00 ratio. Also, I read somewhere that Ford was putting 8.8" rear ends into these particular years of f150's.

I'm not saying you're wrong Steve83, I'm just looking for a second opion.
Also, is this the kind of info that would be found on the axle tag?
The tag on the rear end reads:

S316D
3 00 9 5004

I can't tell if the first number in the last set of digits is a 5 or S.

 

You forgot to tell us your tire size. It makes a difference. If you're running 235/75-15s, they roll at about 722 revs per mile.

At 60 MPH you'd be turning 2166 RPM with a 3.00 gear and about 1985 at 55. I'm guessing you're running a slightly shorter tire or that ypur speedo is off by a hair. Either way it sounds like a 3.00 rear to me.

 

Okay. That is pretty close. I am running 235/75-15's. My speedo must be off a hair. I'm about 100 rpm's higher than what you listed. That 722 revs per mile was the number I was missing in trying to figure it out. One more question, how do you calculate that 722 revs per mile number?

Thanks strangeranger!

Hope I didn't dis you any steve83, but I had to ask around.

 

The 9 on your tag is 9" rear, 3.00 is the ratio if it was limited slip there would be a L in place of the dedimal like this 3L00. In 83-86 both 8.8" and 9" axles were available.

 

You actually can't calculate it. I looked it up at www.tirerack.com IIRC I used Bridgestone's data. The manufacturers vary from about 720-725 except for Dunlop who typically run a very different number for all their tire sizes.

 

I don't mind - I make mistakes just like anyone else. (Maybe more...)