Hello; I have a 69 Firebird Conv. and want to replace my 10 bolt rear end that has a uni rear end with a bent axle. My hope is to replace it with a 12 bolt posi unit. Does anyone have suggestions on do's and don't for this project? I would like to install rear disk brakes at the same time.

Thank You,

The 12 bolts are going fairly high in price due to their being original equipment on the rarer 1st generation Camaros. You will be paying extra for the collectibility factor. And a 10 bolt can easily be built to withstand the abuse just about anyone can dish out on a 69 Firebird convertible.
If you are dead set on a 12 bolt then you will find it's a very straightforward swap. Since they were original equipment on the Camaros, all the parts are available for the swap. I believe that your original driveshaft will have to be shortened but the conversion u-joint is available... You may be lucky enough to find a Camaro driveshaft that would bolt right up.

This is an interesting topic as I have never understood the need to change to the 12 bolt. If people could see how I beat my car and the way I take off and that ole 10 bolt holds up just fine.

What is the advantage to the 12 bolt?

If you break something, parts are usually less expensive, and easier to find.

I am having this dilemma myself! I have left the rear until last as everyone has an opinion on the BOP 10 bolt, and I am completely on the fence! Sink a 1K in the BOP or go for the 8.5" nova swap for less, or go 12 bolt which you might as well go fo the 9" for almost the same $$$

I want to keep the BOP as it is original, but I don't want to fear breaking when out playing!!

I would be really interested to find out what combos some of you are running and maybe some routes not to go?? I don't intend to drag but do enjoy the odd beat session now and then!

Speaking for myself, I have been running the stock 10 bolt for the last 8 years and I have beaten this thing and it has held up all these years. I switched out the 4:56 for 3:55 when I bought the car and I am happy with the setup...

I had a 10 bolt in a 69 coupe that I ran at the track. Roughly a 500HP car with nitrous. The 10 bolt held up for 100+ passes and it's still cruisin' the streets. The key is to have a 'tight' set-up. Slop magnifies wear and tear.

I did a 2nd gen 8.5 corporate swap with new perches relocated and a 3.42 posi gear. very happy with it.

The 8.2's are stronger then most believe.
Had both a 3.23 and 3.36 posi for years without problems.
The issues usually begin with 500 HP with A/T's and slicks.
About 450-500 with M/T's and slicks. Traction being the killer.
High milage not included.

And if you lucky to find a HD 4-pinion BOP 10-bolt...

I need to swap out my gears on my 10 bolt, 2.56 just is too tough in the city on the clutch, altho great on the highway.

Any suggestions on how to go about it, ie buy new pinion and gear, or used....and are they pretty interchangeable or are they year/era specific?

Don't really need posi as I don't drive it too hard, altho would be a nice bonus if one can be located and can be fitted...

So say a BOP with a powertrax unit or locker with a ta rear cover that supports the main caps should hold up well to some abuse behind +/- 350 hp

You could pop across the line to Ricks Ring and Pinion. You're definately close enough Everett, WA

I have heard the Yukon gears are a little nicer for drivers as the richmond gears like to make a little more noise...

You will need the spacer if you use your existing carrier once you go over 3.23 or 3.36 i can't remember...

I have been told to be careful with the used posi's as typically they are the cone type and after 30+ years are usually getting close to the end of their lifes

Don't want to go over 3.36 so thats good. Does Ricks do the install as well....be a good excuse to visit Brett as well....

David,
Don't go for a used ring & pinion... new only.
The ring & pinions are not year / era specific, they're model (i.e. 10 bolt, 12 bolt) specific.

I think Fuhrmann is referring to Randy's Ring & Pinion in Everett.

Trevor

I can guide you through this if you decide to DIY. Trevor is right, you want new parts....

Auburn Pro posi and Richmond 3:55 gears. 400+ HP. Very happy! Haven't tried it on the track...yet.

I did my own. Bought the Richmond gears on line and printed and followed step by step instructions off the internet. After I had it done I was so unsure of what I had done so I took it to a shop to have it looked at. Shop called me an hour later and told me I had installed and set everything dead on.

I was shocked as I had no dial guages or any real tools to speak of. Just a matter of taking the time and lots of patience. I remember using the paint that they give you and having to pull things apart a couple of times to get everything correct etc.

Yes Randy's.... Randys

I'm losing it!! I beleive they will install but do not know fore sure!

I will locate new gears, do the internet review....and advice from Jim and y'all...thanks. Be nice to get some better gearing in her.

If you order your parts from Summit or Jegs, make sure the rep knows you need BOP parts. The aren't as knowledgable as you may expect...Have your catalogue in front of you to verify part numbers.

Get an extra crush sleeve...just in case.

Summit sent me a chebby pilot bearing for my bird. Don't blindly trust them.

I bought a used 8.5" 10 bolt Nova posi rear that had been professionally rebuilt by DTS with 12" Disc brakes for a grand. Guy was switching to a 4-link suspension that used a 9" rear.

I had my 10 bold converted to a 3:55 posi, Eaton gears. Nice and tough. It works just fine.