I have a 1972 Chevelle with standard size tires and i think the orginal 10 bolt with 3.08 gears. I was wondering what the strength of them are. I am going to putting a posi in it with 3.73 gears of 4.10 gears. I have a SBC .60 over with decent cam and 650 Carter carb. I was also wondering about upgrading the axles to make it stronger. I am trying to save money and i cant find any 12 bolts. Any advice is much apperciated

What are the plans for the Chevelle? If it's going to be a street car, the 10 bolt will be fine. Even on the track there's stories of 10 bolts outliving transmissions and stuff, but the 10 bolt isn't really recommended there.

I think I've heard rumors of some '72's having the 8.5 10 bolt out back. Check to see if you have that, if you do you're good to go.

Also, changing the gears and adding a posi isn't really a job for the novice. Do you plan on doing this yourself?

Scroll down to see the pics of 8.2 and 8.5
http://www.chevellestuff.com/qd/generic_rear_axle_info.htm

Take a look at this web site!

www.superchevy.com/technical/engines_drivetrain/driveshaft_rearend/sucp_0812_chevy_10_bolt_rearend_upgrades/photo_01.html

and

www.chevyhiperformance.com/techarticles/48518_posi_10_bolt_upgrade_install/index.html

I had issues trying to find a 12 bolt so I stuck with my 10 bolt and beefed it up with a eaton posi, summit axles for disk brakes. As the gentleman mentioned above it is not a job for a novice so I had a good friend build it for me at a low cost. I got to watch and be a gopher, but it was a good oportunity to learn.

You'd have to see which 10 bolt you have. There were two available which made it into vehicles through 1970 to 1972. The 8.5 inch or the 8.2 inch 10 bolt. Prior to 1970, all Chevelles with a 10 bolt were 8.2 inch.
The 8.2 inch has a 8.2 inch ring gear, and a 1.438 inch diameter, 25 spline pinion shaft and is the least desirable of the two 10 bolts.
The 8.5 10 bolt has a 8.5 inch ring gear, and a 1.626 inch diameter 30 spline pinion shaft (same as the 12 bolt).
The combination of 8.5's increased ring gear diameter, pinion shaft diameter, and increased pinion shaft spline count, provides increased strength over the 8.2 inch 10 bolt.
An easy way to determine an 8.5 or 8.2 carrier is the 8.5 uses 10 7/16-20 LH bolts to bolt on the ring gear.
The 8.2 carrier uses 10 3/8-24 RH bolts to bolt on the ring gear.

One last note... don't be tempted to adapt a truck 12 bolt for your car. You'd probably be better off with the 8.5 10 bolt due to the small pinion diameter (1.438") on a truck 12 bolt.

yeah its a 8.5 inch so thats good? and i dont plan on taking it to the tracks. but do you think that an axle upgrade is needed?

If you are going to replace everything in the rear end then I recommend upgrading it to 30 spline axles. This doesn't cost any more than replacing the 28 spline axles. I've built many 8.5 rear ends with 30 spline axles. This upgrade will bring the 8.5 closer to the strength of the 12 bolt.

Yep, 8.5 is good.:thumbsup:

If it's just a street cruiser, the axle upgrade isn't necessary, but it would beef it up. That's something you could upgrade later on if you feel the need for it.

The tires will break loose on the streets before there's enough stress on the rear or axles to harm them. Wheel hop is a different story, avoid that at all times.

I would just put gears and a posi in along with a regular rebuild kit. Your not going to break it on the street with a 350. :noway:

I've run a bunch of 11.1's with my car 1.63-1.72 60ft's with a stock 8.2 3.36 gear posi.

Probably living on borrowed time but no problems so far.

Thanks everyone. but if i wanted to upgrade the axles what brand would you suggest. money no question. but not going to the track

I use Moser axles. They are made to fit. I would use a 30 spline Eaton Posi, 30 spline Moser c clip axles, Timken bearings and a good brand name gear set. I currently sell and install Yukon.

I agree with Freddie, if you put a posi in, get one to match the aftermarket 30 spline axles. Once you've bought the posi unit, you're stuck with that spline count on your axles....unless you buy another new posi. You never know what shape the axles are in after 37 years from previous owners...you may also want to replace the wheel bearings(and seals) if you have significant axle wear there.

Do it once, do it right. Brett just likes to tell people small blocks don't break anything:D.

My 71 SS 454 LS5 ELCO naturally came with a 12 Bolt but orignal owner grenaded it long ago. It had a 8.2 10 bolt w/410's from a Chevelle when I got it. Current carrier had a then new Eaton POSI, 30 spline GM axels and 410 gears and a TA girdle. Seems a shame to remove this one -it wont break even after pulling over 15 passes at 12.99 at the track just to install the date correct 331 POSI 12 bolt