What is the physical difference of a 2 series carrier gear and a 3 series carrier gear of the same ratio. I bought a used one and dont know wich one it is. All I know is that it is 3.23.

thickness of the ring gear. The 2 series is thicker of the same ratio gears. Factory gears are 3.23 and higher-3 series. 3.08 and lower-2 series

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350 with stealth intake, holley carb, 470 lift cam. 700r4 with .5 boost valve, vette servo, tci lock-up kit, B&M megashifter. Richmond 3.73 gears, powertrax locker, timkin bearings, synthetic lube. Custom 3 inch single into 2 2.5 pipes. 1 1/2 drop springs, 1 5/16 solid front sway bar, 1 inch rear bar, custom subframe connectors, custom LCA relocation brackets. Kobel ground FX, current red metallic paint. Lots of other stuff...
82camaro

How thick is the 3 series ones?

Depends on the gear ratio. The higher the gear ratio(number wise), the smaller the pinion must be--since it has to have less teeth. The ring gear must then be thicker to compensate for the smaller ring gear. This is why they have 2 and 3 series gears. If they didn't the 2.73's would have a thin ring gear and 4.11 would be really thick.

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350 with stealth intake, holley carb, 470 lift cam. 700r4 with .5 boost valve, vette servo, tci lock-up kit, B&M megashifter. Richmond 3.73 gears, powertrax locker, timkin bearings, synthetic lube. Custom 3 inch single into 2 2.5 pipes. 1 1/2 drop springs, 1 5/16 solid front sway bar, 1 inch rear bar, custom subframe connectors, custom LCA relocation brackets. Kobel ground FX, current red metallic paint. Lots of other stuff...
82camaro

I have a set of 410s for series 2 the ring gear is about 2 1/2 in thick the series 3 410 is about 1 3/4

OK thanks for clearing that up for me.
Time to buy more stuff.