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12 bolt 9.3

Posted: Sat Feb 04, 2012 8:38 pm
by glenn4spgs
I took the cover off a 12 bolt 9.3 today it is a posi and it has 41 ring and 14 pinion = 2.92. In a earlier post the ratio's went from 2.73 to 3.08 and did not mention this ratio.did they make this ratio or is my math wrong? rear is out of 73 riv. GS. Thank's Glenn

Re: 12 bolt 9.3

Posted: Sun Feb 05, 2012 9:26 am
by monzaz
Was there a dash between the 2.73 -3.08 like this? If so it covers everything in between including your 2.93. That is what the carrier (posi) holds...2.73 2.93 3.08 fit that open or posi carirer.

Yes there is a 14 41 which is 2.928 which rounds up to 2.93.

You should have a 12 bolt cover with 12 bolt guts the posi will have a 'S' type spring and square tab clutches. :)

I will reference the other post and correct if needs be. Thanks, Jim

J D Race
Richfield, oh

Re: 12 bolt 9.3

Posted: Sun Feb 05, 2012 12:47 pm
by glenn4spgs
Yes there was dashe's sorry. Thanks for this response I have one more car I think is posi and riv 12 bolt 9.3 what should I ask for the 2.93 want to be fair dont need as I am building a 65 skylark gs thinking about one of moser's 9inch unit's. what is the difference in width between the a body rear ends between the years? I have a 12 bolt chev in my car now has very low gears going to pull cover and inspect maybe you could set me up would like in mid three's. maybe trade on these three rears? Want rear disc brakes.Thank's Glenn!

Re: 12 bolt 9.3

Posted: Sun Feb 05, 2012 4:22 pm
by monzaz
Well the 1965 a-body is 54.25" from housing end flange to flange

The 1968-1972 rears are 55.25 from housing end flange to flange.

So your only talking 1/2" on each side - either width 12 bolt will bolt right into your car. Disc brake kit is available for the 2 bolt too. we have them for 395.00

What will you be doing with the car that you think you need a 12 bolt rear.

If you have the 12 bolt in the car now and it fits just build that.

I do not even build 9" rears that is how much respect i have for those rears. JUNK. Only good 9" is the pro pig. Anything with the stock 9" pig or gears set is a basic 10 bolt rear. Sorry But that is what it is It is a 10 bolt by any other name. 10 bolts hold the ring in place and that is what it is.

If you have a posi already in the 12 bolt you can use it add gear set( 3.42 3.55 3.73) rebearing it because of AGE of the rear. DEFINITELY BUY GOOD 30 SPLINE AXLES (we have them for 220.00 a pair) They will hold to 500+ HP / torque. Even at the track with stickys. If the car is street bound 80% of the time - DO NOT c-clip elim the rear. waste of money and time. New axles will hold the power just fine.

2.93 rear with posi all depends on the person that needs it. 300-400 as is condition used unchecked etc. Most want the 3.23 3.42 rear...harder to find.

JD Race