10-bolt question 8.2 types versus 8.5

I thought about PM'ing Monzaz, but figure a thread might help someone else down the road.

I found on another forum some 4.56 gears for sale but am unsure if I have a carrier that will fit their application. Namely, the difference in the Chevy 8.2" and the Pontiac 8.2" (for my '69 Firebird).

This is essentially the ad. I have a '69 Firebird that I believe has the stock rear end, and estimated 3.08 gears. I also have an 8.5" carrier (with a different axle housing) currently with 3.42 gears. Will these richmond gears fit either of the carriers I own?

As a side question, can an 8.5" carrier be installed in an 8.2" axle housing?

Thanks.

 

I would say no only because there is a size difference between the two carriers housing's

 

I don't think anything but the backing plates and the housing bolts will interchange between an 8.2 and an 8.5 of any type.

If you have 8.2 under your firebird, does it have the torque or track bar that I've seen under some?

 

I have not verified that the rear end in my Firebird is stock, but a stock rear end would house 8.2 gears. It's a muli-leaf rear end with no track or sway bars.

 

I think you need to narrow your question down to one at a time here. 4.56 gears or 8.2 differences or what you have in your Firebird. Jim

I would start with the IDing of the diff in the Firebird.

Shoot some pictures of the rear cover.

J D

 

Here are some pictures of the rear end.

 

I think, but Monzaz is the de facto expert, you have a an 8.2 Chevy from the looks of the cover.

With what I believe about the 67-69 F body, you should be able to put a Chevy 12-bolt out of a Camaro under it. An 8.5 from a later X-body would probably be a direct swap, save u-joint and/or drive shaft length variations.

 

That is correct. Only thing is the perches look like they have been swapped to MULTI leaf perches.
10 bolt 8.2 CHEVY rear.
Specs are 25 spline pinion - 1.438 Pinion shaft -ring gear diameter is nicknamed 8.2 but really measures 8.125.

This rear will handle the street just fine and some track runs with OUT SLICKS. You start hitting this with slicks over 350 ft lbs lower than 2500 RPM and stickies you could have a mess.

Now 8.5 carrier can not be used in the Chevy 8.2 rear... JUST WILL NOT WORK. I have seen the posi units in the BOP bolt in axle pontiac rears BUT even then the 3 series 8.5 carrier can only hold the 2.56 2.78 gears so REALLY what is the point.

IF you have a 3.08 gear in the CHEVY 10 bolt you are good for all the steep gears meaning 3.36 3.55 3.73 4.10 4.56 4.88 5.13 will all fit the carrier in the rear.
IN Pontiac 3.08 is the MID series carrier and is different than the chevy carrier ring gear land measurement (reference picture below)

10 bolt chevy rear end will be 54.25 (or 60" drum to drum over all rear width) that is 1" narrower than the Firebird 10 bolt 8.2 rear of the same year era. Firebird is 55.25 and 61" over all width.

Hope I answer all or most of the questions. I can also help with parts if you need. We can quote you out some prices to take around and compare. Jim

 

Thanks a ton for the information! So if I read this right, it IS a Chevy 8.2 so I should be able to purchase these 4.56 gears? The positraction carrier is also tempting... What's the going rate?

I have the old 8.5 posi traction rear axle out of my 1977 Skylark (x-body) from when I swapped the 9" into the Skylark as my back up plan. For now, and the next year or more, it's a naturally aspirated straight six with a 2004r trans.

 

DO THE 8.5 10 bolt we can make that strong as a 12 bolt easy. Jim