What gears and rear end do I have?

[Mo Power]

Well I have a 73 Charger SE which had an orginal 400 but now a 318 and I'm sure the rearend is stock. But I know it's 8 3/4 but I'd have to take a guess of 3.23 gears or lower. Because I looked on the broadcast sheet and it says for axle 980.

[OttawaCharger]

Since you have the broadcast sheet, there should be a code for rear end gearing as well.  At least my '68 had that.
Also, the rear ends came from the factory with a small metal tag that had the ratio on them. 
If none of those work for you, jack up the car and put it in neutral (of course you're going to block the front tires right?? ) now turn the driveshaft one turn and take note of how may turns the wheels make.  That should give you your ratio.

[Mo Power]

Well if I did jack it up and turn the driveshaft I doubt I would know what gears I have by just doing that because I'm clueless on how that helps.

[konigcharger]

your looking in the wrong spot........... row 2 column 4 axle D??

[Ghoste]

Fender tag should have it too but you still won't know unless you are certain it's the original.  To do it by counting, if one part turns a single revolution and the other portion turns about 3 and 1/4 times, then you a 3:23.

[OttawaCharger]

To do it by counting, if one turns single revolution and the other portion turns about 3 and 1/4 times, then you a 3:23.

That's what I meant. 

[konigcharger]

Fender tag should have it too...

not on the fender tag in 73 only the bs 

[Ghoste]

That sucks.  I suppose by 73 there were a lot fewer optional axle packages ordered or even available.

[konigcharger]

only 8 1/4 or 8 3/4

tallest gears you could get was 3:55

[Ghoste]

Welcome to the energy crisis. 

[Mo Power]

Ok for Axle D it says 51 so what is that?

[69XP383]

Mo,

I had the same problem as you did. If you go to mymopar.com and click on fender tag codes you can get print of the codes that correspond to the fender tags and broadcast sheets for the year of your vehicle. I just looked up code D51 and it shows it to be a 2.76 rear axle ratio problem is it shows it for 69-71 vehicles; I'd double check to make sure it's the same for a 73.

If you cant find the codes, do like Ottowa said, I had to do it as well. Place a jack under the car; I put the jack right below the center of the housing for the rear end. Have someone help you if needed, and turn a wheel one full turn. As you do this, count the number of times the yoke/u-joint turns in relation. When i did it, one full wheel turn was counted to be what a friend called 3.25 turns on the yoke/ u-joint.

We guessed it was a 3.23 since no 3.25 was ever made. If you turn the wheel one full time and the yoke turns about 2.75 turns, you can assume you have the 2.76 axel.

[69CoronetRT]

Ok for Axle D it says 51 so what is that?

2.76

[konigcharger]

2.71:1 on 72 and up

are you sure its an 8  3/4 

[hemihead]

Probably an 8 1/4.

[Mo Power]

Well I'm not sure I guess I was just assuming it was 8 3/4 rearend but I could be wrong.

[Ghoste]

If there is a cover on the back of the housing that you remove to access the gears, it is an 8 1/4.  If the housing appears to be one solid piece when viewed from behind and the only bolts are on the front of it so that the diff assembly slides in as a complete unit, it is an 8 3/4. (in this case)

[Mo Power]

Ok checked today it has bolts on back of housing to view gears so it's a 8 1/4 rearend what gears are you able to have for it? And what would mine most likely be?

[Ghoste]

D51 means it should be 2:71.