As stated I have an 1980 F-100 and it has a 9" rear and the tag stamping is like this.

DM-CL 0C05
75 9 S310B

When I googled decoding a 9" it actually brought me back to this site but in the 87' to 96' truck and some of this looks the same but some didn't so I thought maybe if I checked in this series of truck it might help. Thank you.

 

You are missing the first digits, which I think are "W" and "2".

<table style="border-collapse: collapse;" id="table1" border="1" cellSpacing="0" cellPadding="2" width="98%"><tbody><tr><td bgColor="#fae9d1" rowSpan="2">WDM-CL</td><td>Ford F100, F150 Pickup '79</td><td align="center">2.75</td><td align="center">9 in</td><td align="center">NL</td><td align="center">28</td><td align="center">-</td></tr><tr><td>Ford F100, F150 Pickup '80-'82</td><td align="center">2.75</td><td align="center">9 in</td><td align="center">NL</td><td align="center">31</td></tr></tbody></table>

 

WDM-CL = 9" rear axle / 2.75-1 / No Limited Slip.

0C05 = Assembled March (C) 5, 1980 (0).

 

Thank you both for the replies, it's a pretty plain truck so I figured it wouldn't have anything to special..... but I was hoping.

 

Unless you have an I6, look for a different set of gears. My 80 had a 302 with those 2.75's. It was fast, but 0-60 was like 3 years or so.

 

Worst gears ever. Great for MPG's though!

 

Not quite. The 2.47 ratio gears take top honors for lousy gearing.

 

Good for mileage yes, but why it wasn't set up with an AOD and 3.55's instead is beyond me.

 

That truck will buzz right along on the interstate at 70-75mph along with all the modern cars and trucks with that gear.

By the way it never fails. When I saw the "75" in your post I guessed it was a "2.75". They always punched the bolt hole into the first digit, wiping it out.

 

OP's F100 is a 1980, AOD wasn't available in F100/150 until 1981...and then initially...only w/a 302.

 

On top of that, 3.55 ratio gears weren't offered in a 9", just the 8.8", which didn't come along till 83.........
3.50 gears were, though.......

 

Franklin2, thanks, I crawled back under and I couldn't find that W or the 2 mentioned earlier but I figured they were right anyways.

I have an AOD and a 302. Haven't decided if I'm going to keep it or change the motor and flip it.

 

If you have AOD, your truck is a 1981 or it was swapped in.

AOD introduced in 1980 LTD/Grand Marquis/Town Car/Thunderbird Cougar/Mark VI & 1981 F100/150 302.

Here's the 1980 F100/350 & Bronco (U) A/T application chart. Where is the AOD? No see um.

 

It was just a thought. They already HAD the AOD in production, why not use it. Gearing was similar to a C4/C6. You'd have the advantage of a lower first gear ratio, and OD I would imagine would keep the revs in the same range as the higher gearing. An AOD with 2.75's though, that's a terrible idea.

 

Also, I seem to remember coming across a few '80 models with AOD's. Could have been swapped, sure, but I don't always trust the parts catalogs, they have been wrong before. Especially on the 1980 model year.