Rear Axle Ratio
 

Just found thisdd site and registered today. Have a'92 F-150, 5.0 engine, Automatic, with 134,000 miles. I only get 13 mpg around town and think the differentail ratio is to steep. I think the "trailer package" came with a ration somewhere in the 3.75 range. I also think a 3.53 ratio is available. Any have expierence in this field? Sure would like some help in trying to improve my mileage. Rairly tow a light weight trailer very short distances(les than 50 miles)
Thanks for any help or suggeations.
See Ya!
Tony

There's a sticker on the driver's side door jamb that will tell you your ratio.
18= 3.55
19=3.08
H8=3.55 limited slip
H9=3.08 limited slip

Changing the gears will cost you about $1000 per axle (front too, if it's 4x4). So take that into consideration. Also, even if you swap to 3.08 gears, you can expect maybe 3-4 mpg improvement. I said MAYBE. :)

actually you can buy gear, ring, and pinion sets from summit racing for 180 bucks.

Yes, but unless you've done it before, or have someone who knows what they're doing to help you, I wouldn't recommend it. The margin for error is too small - there's no "close enough" or "almost". It's either dead on, or completely wrong.

I had this same inquiry in the Clutch, Trans, Differential,[/U] etc[/U] forum. Was advised to check the metal tag attached to the differential cover. It will give you a lot of information that you can reference. In my case, it was a lifesaver. The door in not orig and would have thrown me off.

[QUOTE=andym]There's a sticker on the driver's side door jamb that will tell you your ratio.
18= 3.55
19=3.08
H8=3.55 limited slip
H9=3.08 limited slip



Isnt H9 3.55 LS and H8 3.08 LS. I could be wrong on this?

Do those codes apply regardless of year and model? I would assume so. But, then there is that word "assume" again.

Thanks

Check the tech section for Ford Axle codes in this site. They are all listed.

... confusion level rising...

Here is a clip from the article I found in the tech section.

Axle Decoder Chart

Code Ratio Capacity Maker Type Yr

12 2.73 3800 FORD REG 1991
17 3.25 3300 FORD REG 1971
17 3.31 3800 FORD REG 1995
18 3.08 3800 FORD REG 1991
19 3.55 3800 FORD REG 1991


But, the postings in this thread call for the 18 code to be 3.55 and the 19 to be the 3.08. I hate to come off as a grammar lawyer. But, I am trying to learn and understand.

If the code on the door on my truck is 18. Which ratio am I running?

Thanks and sorry for being picky.

Okay, on this page, top right in Blue letters, TECH ARTICLES, to top left in grey area, DECODERS, CODES, CHARTS, to FORD AXLE CODE CHART. 18 = 3.08.

so 19 is 3.55? i guess i dont have 3.08's. i was wondering why my speedo shows my speed at 5 mph faster than what im actually going.

Here you go Tex94!

Code Ratio Capacity Maker Type Yr

12 2.73 3800 FORD REG 1991
17 3.25 3300 FORD REG 1971
17 3.31 3800 FORD REG 1995
18 3.08 3800 FORD REG 1991
19 3.55 3800 FORD REG 1991
25 4.10. 5300 FORD REG 1991
29 3.55 5300 FORD REG 1991
35 4.10. 6250 FORD REG 1991
36 3.73 7400 DANA REG 1980
39 3.55 6250 FORD REG 1991
45 4.10. 7400 FORD REG 1991
49 3.55 7400 FORD REG 1991
65 4.10. 8250 FORD REG 1991
69 3.55 8250 FORD REG 1991
72 4.63 11000 DANA REG 1991
73 5.13 11000 DANA REG 1991
H5 4.10. 3800 FORD LIMITED SLIP 1991
H7 3.31 3800 FORD LIMITED SLIP 1995
H8 3.08 3800 FORD LIMITED SLIP 1991
H9 3.55 3800 FORD LIMITED SLIP 1991
B5 4.10. 5300 FORD LIMITED SLIP 1991
B9 3.55 5300 FORD LIMITED SLIP 1991
C5 4.10. 6250 FORD LIMITED SLIP 1991
C9 3.55 6250 FORD LIMITED SLIP 1987
D5 4.10. 7400 FORD LIMITED SLIP 1991
F5 4.10. 8250 FORD LIMITED SLIP 1991
W5 4.10 8250 FORD LIMITED SLIP 1995

i know ive posted here 3 times in a row, but im confused.

the origninal axle in my truck was 19 (3.55). but the guy i bought it off of put in a new rear end, and i dont know what it is, alls i know is that the speedo shows at 5 mph too fast. does that mean theres 3.08s' or 3.73's, or its because my aftermarket C-6. it used to have the mazda 5 speed.

sorry for the added confusion.

This has side tracked a little. What about the original question? What sort of upgrades are in order?