Rear Axle Code - Chevelle Tech
Transmission & Driveline Transmissions and Differentials

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post #1 of 21 (permalink) Old Aug 18th, 19, 10:28 PM Thread Starter
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Rear Axle Code

So I finally got under the car and sanded off 50 years of gunk and undercoating. I got this code off the rear axle: FJ0325

So my understanding is that is 3.08 ratio that was made on March 25.

I know it is a 10 bolt. Not sure how to figure out what size. Wondering where to go from here. Just had the engine rebuilt and have around 400 horses to play with.


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post #2 of 21 (permalink) Old Aug 18th, 19, 10:49 PM
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Re: Rear Axle Code

It would be much easier to help if you include what year car you are working on. A photo from the rear showing housing would be good too., try this to help:
https://www.crankshaftcoalition.com/...identification

1970-LS5, #28- Fathom Blue,TH400, original motor car.
1970- NOM, 496, M21, #48 Forest Green.
1972- Malibu, 350. TH350- original motor car, #43 Gulf Green.
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post #3 of 21 (permalink) Old Aug 18th, 19, 11:17 PM Thread Starter
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Re: Rear Axle Code

Quote:
Originally Posted by 70SSTHUMPER View Post
It would be much easier to help if you include what year car you are working on. A photo from the rear showing housing would be good too., try this to help:

https://www.crankshaftcoalition.com/...identification


You are right. I should have taken one. For sure a 10 bolt. I will take one soon. Only pic I took was of the stamp but I think it isnít helpful.

The car is a 68 Malibu. Originally had a 307 in it with a power glide.


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post #4 of 21 (permalink) Old Aug 19th, 19, 7:51 AM
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Re: Rear Axle Code

If the rear end hasn't been change then it's a 8.2 10 bolt. All '64 to '72 Chevelle 10 bolt rear ends were the 8.2. Many parts got changed in these cars over the last 50 years, so it could have been swapped.
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post #5 of 21 (permalink) Old Aug 19th, 19, 9:40 AM Thread Starter
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Re: Rear Axle Code

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Originally Posted by big gear head View Post
If the rear end hasn't been change then it's a 8.2 10 bolt. All '64 to '72 Chevelle 10 bolt rear ends were the 8.2. Many parts got changed in these cars over the last 50 years, so it could have been swapped.


I doubt it was swapped. I guess itís possible. This picture doesnít help much but it was the best I could do with it on the ground.


Is there any point to upgrading an 8.2? Or should I just go for something else. I have a lot of other priorities over dropping $3000 on a 12 bolt.


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post #6 of 21 (permalink) Old Aug 19th, 19, 11:05 AM
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Re: Rear Axle Code

Unless you plan on slicks and trying to hook it, no reason to upgrade.
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post #7 of 21 (permalink) Old Aug 19th, 19, 12:14 PM Thread Starter
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Re: Rear Axle Code

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Originally Posted by 427L88 View Post
Unless you plan on slicks and trying to hook it, no reason to upgrade.


Didnít know about getting a bit higher gear ratio.


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post #8 of 21 (permalink) Old Aug 19th, 19, 12:19 PM
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Re: Rear Axle Code

Make sure it counts just over 3 turns of the driveshaft for one rotation of the tires. Dont assume.
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post #9 of 21 (permalink) Old Aug 19th, 19, 5:37 PM
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Re: Rear Axle Code

That is the 8.2 10 bolt. Someone got a little sloppy with the sealant.
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post #10 of 21 (permalink) Old Aug 19th, 19, 6:45 PM Thread Starter
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Re: Rear Axle Code

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Originally Posted by big gear head View Post
That is the 8.2 10 bolt. Someone got a little sloppy with the sealant.


Do you think it is worth upgrading to a 3.55 or 3.73 from a 3.08 with that?

Hehe, someone got a little sloppy with a lot of things on this car. Realized yesterday the bolts for the sway bar bushings/connects arenít the same. Passenger side spacer spins freely and has about 1/4 to 1/2 of play in it. The one on the driver side, which I assume is the correct one, is right and doesnít have play in it. One is a coarse thread and one is fine.


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post #11 of 21 (permalink) Old Aug 19th, 19, 7:56 PM
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Re: Rear Axle Code

Since someone's already been inside that rear ,pull the cover and see just what gears are in it and what condition everything's in.
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post #12 of 21 (permalink) Old Aug 19th, 19, 10:26 PM Thread Starter
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Re: Rear Axle Code

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Originally Posted by Mike View Post
Since someone's already been inside that rear ,pull the cover and see just what gears are in it and what condition everything's in.


Will I be able to see stamps on the gears or just count them?


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post #13 of 21 (permalink) Old Aug 19th, 19, 10:50 PM
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Re: Rear Axle Code

Tooth count and GM numbers (assuming GM gears) are stamped on gears.
Example
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post #14 of 21 (permalink) Old Aug 20th, 19, 12:09 AM
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Re: Rear Axle Code

Everything really depends on what your goals are with this car: street, strip, road track, cruiser? With 400 ponys ( i suppose thats flywheel?) not rwhp. If its just street with a little fun I wouldn't hesitate to put a little money into your 10 bolt. I did, 1972 Chevelle, 350/350 3:36, posi, new bearings and seals, hardened axels, girdle, and brakes for less than 1K. Huge difference, great low end, stomped on it a few times - feels fantastic and moves the car pretty well. Don't underestimate that 10b.
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1970-LS5, #28- Fathom Blue,TH400, original motor car.
1970- NOM, 496, M21, #48 Forest Green.
1972- Malibu, 350. TH350- original motor car, #43 Gulf Green.

Last edited by 70SSTHUMPER; Aug 20th, 19 at 12:17 AM. Reason: add photo
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post #15 of 21 (permalink) Old Aug 20th, 19, 12:15 AM Thread Starter
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Re: Rear Axle Code

Quote:
Originally Posted by 70SSTHUMPER View Post
Everything really depends on what your goals are with this car: street, strip, road track, cruiser? With 400 ponys ( i suppose thats flywheel?) not rwhp. If its just street with a little fun I wouldn't hesitate to put a little money into your 10 bolt. I did, 1972 Chevelle, 350/350 3:36, posi, new bearings and seals, hardened axels, girdle, and brakes for less than 1K. Huge difference, great low end, stomped on it a few times - feels fantastic and moves the car pretty well. Don't underestimate that 10b.


Thatís all Iím after. No track for me. Street and getting on it here and there. When I get time I will pull the cover off and see what is there. Thanks for your info.


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