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#1
02-03-2026, 12:39 AM
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Rear end ID help needed
All, I'm looking at a rear axle, and need help id'ing it.
Casting number is N 1235542. Stamping on the axle tube is JA G279 1 Wheel mounting surface width is 60". I have no info on perch to perch width. Looks to be an 8.5, but I am having trouble nailing down whether it is a Nova rear end, or a 2nd gen rear. Target vehicle would be my 67 Firebird, which is already running a Nova rear end with 3.73's. JA looks to be 2.73's, which would be a killer cruising gear. Any help appreciated, thanks!
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"...ridge reamer and ring compressor? Do they have tools like that?" |
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#2
02-03-2026, 11:49 AM
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If your 3.73 rear is posi I bet the 8.5 2.73 is not if that matters to you?
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Wernher Von Braun warned before his retirement from NASA back in 1972, that the next world war would be against the ETs! And he was not talking about 1/8 or 1/4 mile ETs! 1) 1940s 100% silver 4 cup tea server set. Two dry rotted 14 x 10 Micky Thompson slicks. 1) un-mailed in gift coupon from a 1972 box of corn flakes. Two pairs of brown leather flip flops, never seen more then 2 mph. Education is what your left with once you forget things! |
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#3
02-03-2026, 04:48 PM
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No, this rear end is not posi. My 3.73 rear IS posi. Yeah, not ideal, but price is right.
Trying to get a perch center to center measurement. If a Nova rear, awesome. If 2nd gen, then I will likely skip it. A 2.73 would drop my cruise rpm on the highway by a good 1000. 3.73's are a blast, but not great for distance driving, and that's what I am looking more toward doing.
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"...ridge reamer and ring compressor? Do they have tools like that?" |
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#4
02-03-2026, 05:32 PM
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That’s a big change in cruse rpm, where does your Cam’s power band start to haul nice?
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Wernher Von Braun warned before his retirement from NASA back in 1972, that the next world war would be against the ETs! And he was not talking about 1/8 or 1/4 mile ETs! 1) 1940s 100% silver 4 cup tea server set. Two dry rotted 14 x 10 Micky Thompson slicks. 1) un-mailed in gift coupon from a 1972 box of corn flakes. Two pairs of brown leather flip flops, never seen more then 2 mph. Education is what your left with once you forget things! |
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#5
02-03-2026, 08:02 PM
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Around 2000 rpm it starts to scream. It's a little bit cammed up for a 350. 10 years ago, chasing that extra .1 of E.T. was my rage. Not so much anymore
I looked under my car, and the casting on the pumpkin is a 1235542, from a 73 Nova IIRC. So at least that part matches. Is there a definitive way to tell by codes and stampings if an 8.5 is a Nova or 2nd gen rear?
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"...ridge reamer and ring compressor? Do they have tools like that?" |
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#6
02-03-2026, 08:44 PM
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Find a camaro/nova site and see if they have the codes.
Some codes were just for camaro or just for nova. I'd have to search and see if I have them. 
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John Wallace - johnta1 Pontiac Power RULES !!! www.wallaceracing.com Winner of Top Class at Pontiac Nationals, 2004 Cordova Winner of Quick 16 At Ames 2004 Pontiac Tripower Nats KRE's MR-1 - 1st 5 second Pontiac block ever! W.E.C moment "Every man has a right to his own opinion, but no man has a right to be wrong in his facts." "People demand freedom of speech to make up for the freedom of thought which they avoid." – Socrates |
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#7
02-03-2026, 08:51 PM
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Found this on the Nova site
Absolutely the most fool proof way. Stock 68-74 Nova 12-bolt/10-bolt rear axle width is... 60.25" wheel mounting face-to-wheel mounting face, including drum thickness 53.25" backing plate flange-to-backing plate flange 42.75" center-to-center on the leaf spring perches. |
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#8
02-04-2026, 06:43 AM
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There is no casting date on center section?
JA is usually a '73-4 Nova coded 2.73:1, non-posi.
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So long, farewell. |
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#9
02-05-2026, 03:25 AM
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Quote:
Funny enough, I crawled under my ride, and found my current rear end is JA code, with similar dates. So it amounts to an almost identical rear to what I have, minus the posi and upgraded Currie axles. It's been a while since I built that setup. I'm gonna pass on it, let somebody else have a crack at it. Steve brings up a good point about power band. I would be probably better off seeking an OD trans in the future to get my cruise rpm's down. Thanks, all!
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"...ridge reamer and ring compressor? Do they have tools like that?" |
| The Following User Says Thank You to Squidward For This Useful Post: | ||
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#10
02-05-2026, 06:06 AM
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From charts that I have the drop in rear wheel torque when going to 2.73 gears would be a big 27%, and all for a gain of about 10% in fuel mileage on level ground.
Like you posted, a trans swap would be the way to go.
__________________
Wernher Von Braun warned before his retirement from NASA back in 1972, that the next world war would be against the ETs! And he was not talking about 1/8 or 1/4 mile ETs! 1) 1940s 100% silver 4 cup tea server set. Two dry rotted 14 x 10 Micky Thompson slicks. 1) un-mailed in gift coupon from a 1972 box of corn flakes. Two pairs of brown leather flip flops, never seen more then 2 mph. Education is what your left with once you forget things! |
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