How to tell the difference in a 2/3 Series Carrier

I have a carrier from a 98 ls1. It came out of a rear axle with 3.73 gears in it. I am not sure what gears the car had form the factory, the car was an auto. I am wondering if there is a visible difference in the 2 carriers or not.

If it came from an A4, it could have had a 2 series(2.73) or 3 series(3.23). The fllange that the ring gear mounts to would be thinner on the 2 series by about 5/16". You would have to eyeball them side by side or know the measurements, I don't.

anaik pretty much nailed it there. If you could find out what the original ratio was, then you'd know (2.73's or 3.23's). The only thing is, the flange isn't a different thickness, it's just offset by that ~5/16". If you could put it beside your original carrier (which is a 3-series if it's from your M6 w/3.42's) and compare where that flange is, then you could tell. If they're even, it's also a 3-series. If the flange would be such that it's 5/16" further to the left side of the diff housing, then it would be a 2-series carrier (they're made this way to accommodate larger pinion gears of higher ratios).

anaik pretty much nailed it there. If you could find out what the original ratio was, then you'd know (2.73's or 3.23's). The only thing is, the flange isn't a different thickness, it's just offset by that ~5/16". If you could put it beside your original carrier (which is a 3-series if it's from your M6 w/3.42's) and compare where that flange is, then you could tell. If they're even, it's also a 3-series. If the flange would be such that it's 5/16" further to the left side of the diff housing, then it would be a 2-series carrier (they're made this way to accommodate larger pinion gears of higher ratios).

Thanks for straightening that out. I never compared the two. Thought I read what I said somewhere. Sorry if I caused any confusion.

Now I'm confused. Here are some pictures of a 2 and 3 series alongside each other. Clearly it shows a different thickness between the two.

http://www.tacreationsusa.com/differential_carriers.htm

Hmmmm :think:, maybe there's a difference between a Torsen and an Auburn when it comes to that?:shrug: Thing is, I've got a 2-series Torsen (factory 2.73 carrier) and a 3-series Auburn (originally a 3.23 diff that had my 4.10's on it). I've sat the 2 carriers side-by-side on the bench, and it's obvious that the mounting face for the ring gear is offset more for the 2-series carrier. I "thought" that the thickness of that flange was the same on both, just that it was offset differently. Perhaps I'm wrong on that???:confused: ;)

If you put the two different carriers on their sides with the flange in the air, then the 2 series flange will be higher. I can't remember the exact measurements, but the 3 series carrier flange is closer to the pinion. That is why 3 series ring gears are thinner, and need a spacer if they are going on 2 series carriers.

EDIT: Found it

2 series = 5 1/4"
3 series = 4 7/8"

From the ground to the flange.

^ ^ ^ that's with it standing on the "right" side (the end where the right/passenger side axle would slide in), correct??;)

^ ^ ^ that's with it standing on the "right" side (the end where the right/passenger side axle would slide in), correct??;)
Yes. With the flange in the air.