Howdy Yall,


I have a 93 F250 7.3 E40D Auto w/ 3.15 rear gear.
My question has to do with the 3.15 rear gear, is
the 3.15 considered a highway gear or a towing gear.
Any help would be great.

Thanks
Gr8ride

 

I would consider it a High hi-way gear. That is closer to something you would find in a car. 3:50 or lower (higher numerically) in a truck with 3:73 starting the towing gears

 

In Powerstrokes between '94-'97, there were only two gear ratios available: 3.55:1 and 4.10:1. The 3.55's were considered to be highway gears, and the 4.10's were better suited to towing. Are you sure your gears aren't 3.55's? I know yours was built slightly before that, but the gearing might very well be the same.

Quadzilla
'95 F-350XLT Crew Cab SRW 4X4 PSD, 35X12.50X16.5's, Limited slip 4.10's, Hypermax downpipe, gutted EBPV, "Catless" in Seattle, "Renegade" 4" exhaust system, CTFD sticker, Air bags on all four corners, TYMAR intake, shimmed fpr, Diablo Delta chip, Fumoto valve, Autometer pyrometer, Sonnax valve, Tricumulator springs, Tru-Cool, HX mod, Magnefine tranny filter,
4R100 pan, Red Line synthetic in transfer case and both diffs, reverse shackle kit.
And a wish list that gets longer every day.
(Thank God for a wife that likes big trucks.)
For pictures, click here: http://community.webshots.com/user/quadzilla100

 

To the best of my knowledge they dont make 3.15 gearing...
3.73 3.55 3.31 and 3.08(i think) are the only gearing in the 3 range that I know about.

Its probably 3.55's
Rand

 

Assuming your truck has a reliable tach, take the truck out on the highway and run it at exactly 60 MPH in drive (not overdrive), making note of the RPM on the tach. Go home, and measure the rear tire diameter and multiply by Pi (3.1416). Then divide that into the number of inches in a mile (63,360). Divide that dividend into what you were taching at 60 MPH and you've got your axle ratio.
Example, suppose your truck is taching 2550 @ 60 MPH and your rear tires are 28 inches. 28 X 3.1416 = 87.9648. 63360 divided by 87.9648 = 720.28811 -- that is the number of revolutions your tires are turning in a mile. Take your tach reading at 60 MPH (2550 in this example) and divide it by 720.28811 = 3.54025. So your axle ratio is 3.54 to 1.

 

You're absolutely right Joe, as long as they measure the diameter of their rear tires, and not just use the nominal size on the sidewall. My tires are supposed to be 35's, it even says so on the sidewall, but they measure just under 34". That difference could throw the calculation off by about 3%.

Quadzilla
'95 F-350XLT Crew Cab SRW 4X4 PSD, 35X12.50X16.5's, Limited slip 4.10's, Hypermax downpipe, gutted EBPV, "Catless" in Seattle, "Renegade" 4" exhaust system, CTFD sticker, Air bags on all four corners, TYMAR intake, shimmed fpr, Diablo Delta chip, Fumoto valve, Autometer pyrometer, Sonnax valve, Tricumulator springs, Tru-Cool, HX mod, Magnefine tranny filter,
4R100 pan, Red Line synthetic in transfer case and both diffs, reverse shackle kit.
And a wish list that gets longer every day.
(Thank God for a wife that likes big trucks.)
For pictures, click here: http://community.webshots.com/user/quadzilla100

 

Here's the code that's on the
diffs. tag
S 12 9G
10 10 2 3C15
I got the idea that it was a 3.15
by reading this code. Am I reading
it right?


Gr8ride

 

The tag code doesn't mean anything to me.
I agree with Rand -- I am sure Ford didn't offer a 3.15 axle ratio with a diesel engine. 3.23, 3.54, 3.73, 4.10 and 4.55 are what you are likely to see.
Get a pocket calculator and do the math. It is really pretty simple.

 

Sounds like a 4.10 ratio to me. Mine has the bolt head partially obscuring the 4 in the 4.10 so look close to the bolt head and see if you spot a 4. Hope this helps you out.

97 F 250 PSD SC 4x4:-X12

 

s129g is a sterling axel # 4.10 ratio

the lower set of #'s look good except for the first digit is propably blocked.

the first set with just the "10" is 4.10 for the ratio
if it was to read 4L10 the "L" would be for locker then being
a 4.10 locking rearend.

the second set in the bottom row "10 2" is for the ring gear diameter
"10 2" being a 10.25" ring gear diameter

 

60 mph without overdrive???? I think my '97 would blow up !

Thanks for the math, I have been wondering this as well, need more top end !

 

On the sticker on the driver's door, there's an axle code, typically two numbers, or one letter and one number. For example, mine is C5, so from my owner's manual, I can see that it's a 4.10:1 limited slip axle. If anyone wants to post their code, I'll look it up in my owner's manual for ya.

Quadzilla
'95 F-350XLT Crew Cab SRW 4X4 PSD, 35X12.50X16.5's, Limited slip 4.10's, Hypermax downpipe, gutted EBPV, "Catless" in Seattle, "Renegade" 4" exhaust system, CTFD sticker, Air bags on all four corners, TYMAR intake, shimmed fpr, Diablo Delta chip, Fumoto valve, Autometer pyrometer, Sonnax valve, Tricumulator springs, Tru-Cool, HX mod, Magnefine tranny filter,
4R100 pan, Red Line synthetic in transfer case and both diffs, reverse shackle kit.
And a wish list that gets longer every day.
(Thank God for a wife that likes big trucks.)
For pictures, click here: http://community.webshots.com/user/quadzilla100

 

C5 it is...

Have to think about taller gears ...

 

 

You can always do what I did. I went to 35" tires, and they're tall enough to change the final drive ratio to 3.75:1, pretty close to the 3.73:1 on SuperDuties. At 2000rpm, where the best mpg is, I'm doing 68mph. Besides, I like the way it looks.

Quadzilla
'95 F-350XLT Crew Cab SRW 4X4 PSD, 35X12.50X16.5's, Limited slip 4.10's, Hypermax downpipe, gutted EBPV, "Catless" in Seattle, "Renegade" 4" exhaust system, CTFD sticker, Air bags on all four corners, TYMAR intake, shimmed fpr, Diablo Delta chip, Fumoto valve, Autometer pyrometer, Sonnax valve, Tricumulator springs, Tru-Cool, HX mod, Magnefine tranny filter,
4R100 pan, Red Line synthetic in transfer case and both diffs, reverse shackle kit.
And a wish list that gets longer every day.
(Thank God for a wife that likes big trucks.)
For pictures, click here: http://community.webshots.com/user/quadzilla100