So my car was the stock 326 with an open rear end. Now it has a 455 I just put a new quick fuel 750 double pumper on. The thing runs like a striped [censored] ape. But it does desperately need a posi rear end and I’d really like to have like a 3.23 geared posi. So I’m wondering should I buy the components and modify my current rear end or should I buy a bolt in Moser or look for a posi out of an early 70s Nova? I think trying to find an original direct bolt in that I don’t have to worry about is going to be a little more difficult.

So fellow Firebird owners I need your expertise and advice. If anybody has a good bolt in solution for me that’s within 200 miles of St. Louis give me a holler. Otherwise please let me know what you would recommend and where are you would go to get the parts needed to incorporate your suggestion.

Plenty of aftermarket parts available to update your rearend. I'm not sure I've seen 3.23 aftermarket sets available but 3.36 is an option.

Randy's Worldwide

You can also check out here, he may have used parts available:

JDRace

The gentleman who owns that site posts on a lot of the car forums in particular the two I frequent most, Performance Years and V8Buick.

What are the current gears and is it auto or manual? You can get a posi unit installed in your existing rear by a good rear guy

Wouldn't spend a penny on the 8.2 rear end, with a 455 engine.

I'd go at least an 8.5" 10-bolt, or better yet, a 12-bolt.

An aftermarket 12-bolt will be well over $3000, maybe closer to $4000, complete & shipped.

http://www.moserengineering.com/12-bolt-musclepak.item

https://americanpowertrain.com/i-20915258-complete-12-bolt-rear-axle-assembly-for-1968-72-nova.html

https://www.ebay.com/i/261809143940?chn=ps

https://www.currieenterprises.com/12-bolt-custom-rearends

https://www.strangeengineering.net/...-posi-leaf-spring-mounts-no-brakes.html/


Lots of guys prefer a 9" Ford, because of the removable chunk, & wide range of gears & parts available. Might be able to get a complete 9" for a bit less than $3000, from Quick Performance. The base price is $1800. But after you add all the upgrades, plus shipping, you're up to nearly $3k.

https://www.quickperformance.com/GM-F-body-1967-1969-Camaro-Complete-9-Rear-End-Package_p_21573.html

OR, you can locate an 8.5" 10-bolt, out of a '70's X-body, then have it completely set-up, by a rear end expert. Guessing this will cost at least $2000.

OR, you can hope to luck out & find a factory 8.5 or 12-bolt, that has all the stuff you want in it, & is for a reasonable price. The easiest thing to find is probably an 8.5 out of a 2nd gen Bird or Camaro. The leaf spring brackets must be moved in a bit. But, lots of 1st gen guys have done that, thru the years.

Make sure the axle tubes are tack welded to the center section. I learned this the hard way, when the pinion came up thru the floor. 4 good tacks, 90° apart is enuff. I raced several 12-bolts that I did this to. If you try to weld the tubes solid, all the way around, the heat could pull the tubes out of line. I always put 2 small tacks 180° apart. Then added the other 2. Never had a problem doing it this way.

There is always a chance of breaking an axle, and having major problems, when using C-clip axles. For this reason, it's best to not have C-clip axles. But, millions of cars have probably traveled billions of miles, with C-clip axles. We never broke a stock axle. But we were only running low 12 & high 11 sec bracket cars.

Stock axles are plenty tough but they do break. I was at Byron Dragway years ago with a friend and his ‘69 big block Camaro. Car dead hooked and snapped the flange off on the third pass. Low 11 second car. Fortunately it didn’t hurt the car but getting it back on the trailer sucked.

Thanks for the detailed information

Try to find a '71 to '74 X-body 8.5" 10 bolt (make sure it's an 8.5"). https://www.chevyhardcore.com/tech-stories/drivetrain/10-bolt-chevy/

If it's an open differential, I'd install the gears you want and an Eaton Truetrac (helical -gear limited slip). No clutches to wear out. I have one in my truck and I love it. If the posi goes out in my Firebird, it will get one as well.

You mean if the 8.5 is an open rear end? Not put that in my stock unit?

Most of the X-body 8.5 rear ends are one-wheelers (open). Therefore, if you want posi, you'll most likely have to add a new posi unit & the gears you want.

The 8.5 posi & gears will not fit into an 8.2 hosing.

Will an 8.5 from a ‘75 TA work because I just found one

" Will an 8.5 from a ‘75 TA work..."



It'll "work". But the leaf spring mounts will have to be cut off & moved closer together. Springs are farther apart on 2nd gen Birds.

That's why the X-body 8.5's have been mentioned. The leaf springs are the same distance apart as 1st gen springs.

Probably already been mentioned that the driveshaft must be shorter, when replacing an 8.2 with an 8.5.

You didn't say what year your bird is, any 8.5 from 70 up will require a shortened driveshaft by 1", don't be fooled by it fitting, your current shaft will go in but as the car goes up and down on bumps it will bottom out and bend something or somethings. Easiest way to do it is to line up your mounts on the new rear and then cut them off and weld them on in the proper location, or as suggested by a Currie etc all set up but $$$$$$$$$$$$$$$