Rear axle decode

[Rich 71]

I have a 10 bolt in my 71 with     ACC 6100 1 stamped on rear what gear is it

[420ponies]

should be able to see the coding and rear axle ratio in our resources page. It's at the top in the red banner. when it comes up, scroll down to decoding rear axle. It should be in there. my ('72) 10 bolt was a 2:73 posi-traction.

[cny first gen 71]

Jim is right look it up to be sure but if it is a base model it's probably 273 open rear end.

[jft69z]

6 hours ago, Rich 71 said:

I have a 10 bolt in my 71 with     ACC 6100 1 stamped on rear what gear is it

That number doesn't appear to be on the lists.

Can you take a picture of it, should be on the passenger side axle tube, facing the front. Take a picture of the rear cover, and casting numbers too. It's possible it could be a BOP (Buick, Olds, Pontiac) rear diff too.

https://chevellestuff.net/1971/rear_axle.htm

Another thread where someone asked about an 'ACC' code. 

https://www.chevelles.com/threads/rear-axle-code.524321/

[DragCat]

I'd verify the old fashioned way, spin the driveshaft and count spins 🤣 No telling what someone else has done

[Dtret]

I looked also and couldn’t find any definitive information about it. 

[420ponies]

I found something on Wallace Racing . shows a "AC " code (2:78 ratio) from'71-'72 Grand Prix? no other information on that site.