I bought one off ebay years ago, it looks identical to my 2.77 carrier that is in my car now. I thought it would be thicker or thinner or something. Thanks.

 

IDK if that rear even has a carrier break, but if so, the difference will be found easiest if you have some way to measure from the carrier's mounting face to the pinion centerline. A 2-series will have a bigger measurement than a 4-series.

 

It should have a tag that say what gear, or the #s on the left axle tube, or pop the cover off and it should have the gear ratio stamp on the ring. U can count the ring gear gears or rotate the axles and see how many times the yoke rotate when u turn it 1 full turn.

 

Thanks brother, but I just have the carrier not a complete unit.

 

Look at them side by side. One end is the same but the other end of the carrier is different. The ratio is stamped into the ring gear.

 

The difference is how far the ring gear flange is, from the center of the pinion.

There's roughly .400" difference between the 2.

If you set them on a table side by side, on the pass side carrier bearing (the one next to the ring gear flange), and one of em's flange is about .400" above the other, then that one is 3 series, and the one with the "lower" flange is 2 series. If they're the same height and you know the series of one of em, then I'll let you do the math on determining what the other is.

 

OH I forgot...

Here's a pic of the difference. These are 10-bolt ones, but the principle is completely universal to ALL models.

 

Ok, so the ring gear mounting face will be .400 closer to the center? Do I get that right? Thanks.

 

Right; the 3 series flange is .400"ish closer to the center than the 2 series.

In the pic, 2 series on the left, 3 on the right. Plain as day in that particular model. Not sure if it's quite that obvious in the 9-bolt, never have had the 2 side by side to compare.

 

Thank you very much. When I get a chance to look at them again I will measure them. Thanks again.