Rear End Identification - Any Experts? - Pontiac GTO Forum
User Tag List

 
LinkBack Thread Tools Display Modes
post #1 of 4 (permalink) Old 02-09-2015, 12:42 PM Thread Starter
 
Join Date: Sep 2014
Location: Waynesville, oh
Posts: 104
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Rear End Identification - Any Experts?

I am restoring a 1967 GTO and have started at upgrading the rear end. I knew it was an open rear. This weekend I looked into the ratio. Couldn't read the stampings so I counted the teeth, 41/15 or 2.73. Referring to Zazarrine's book I noted 2.73 was not a valid ratio for '67. I originally thought I had an 8.2 BOP 10 bolt, but now based on what I've seen I'm thinking 8.5 GM Corporate. It does have the scalloped cover, but I noticed the rear brake line mount is wrong, the case is tapped on top instead of the bracket that's supposed to come off the top cover bolt. Also noted a big "A" stamp in several places, a sideways "N", and a date code that looks like "924". First character hard to read. Have not found any numbers stamped into the axle tubes yet. Was hoping someone could help me ID this thing.
Attached Thumbnails
Click image for larger version

Name:	rear end 1.jpg
Views:	3191
Size:	55.6 KB
ID:	52153   Click image for larger version

Name:	rear end 2.jpg
Views:	613
Size:	66.8 KB
ID:	52161   Click image for larger version

Name:	rear end 3.jpg
Views:	613
Size:	31.8 KB
ID:	52169   Click image for larger version

Name:	rear end 4.jpg
Views:	444
Size:	10.7 KB
ID:	52177  
goatsnvairs is offline  
Sponsored Links
Advertisement
 
post #2 of 4 (permalink) Old 02-09-2015, 07:15 PM
 
Join Date: Jan 2015
Location: Injun Territory, 'Merica!
Posts: 1,611
Mentioned: 0 Post(s)
Tagged: 1 Thread(s)
Quoted: 121 Post(s)
The rear is the most common of the 3 different versions of the '71-72 8.5 A-body, have built well over 300 as posi rears off that particular style housing. The 8.5 A-body rear has a nodular housing and due to the way it was cast, has more pinion support than any 10 bolt or garden variety 12 bolt. With stock axles in an auto 3500-3700 lb A body, many many have been raced weekend after weekend into mid 11's on slicks. For considerably more strength, have upgraded quite a few A9 & A10 axle bearing versions with new 30 spline Eaton carriers & new custom axles.

Fwiw, in the early to mid 90's , I always ground the big A off these, as well as several other casting numbers. Also reshaped the big square lugs on the bottom to mimic those of an 8.2.
Pinion head is offline  
post #3 of 4 (permalink) Old 02-09-2015, 11:15 PM
 
azmusclecar's Avatar
 
Join Date: Sep 2007
Location: tucson mexizonia
Posts: 50
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
azmusclecar is offline  
 
post #4 of 4 (permalink) Old 02-10-2015, 10:33 AM Thread Starter
 
Join Date: Sep 2014
Location: Waynesville, oh
Posts: 104
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Quote:
Originally Posted by Pinion head View Post
The rear is the most common of the 3 different versions of the '71-72 8.5 A-body, have built well over 300 as posi rears off that particular style housing. The 8.5 A-body rear has a nodular housing and due to the way it was cast, has more pinion support than any 10 bolt or garden variety 12 bolt. With stock axles in an auto 3500-3700 lb A body, many many have been raced weekend after weekend into mid 11's on slicks. For considerably more strength, have upgraded quite a few A9 & A10 axle bearing versions with new 30 spline Eaton carriers & new custom axles.

Fwiw, in the early to mid 90's , I always ground the big A off these, as well as several other casting numbers. Also reshaped the big square lugs on the bottom to mimic those of an 8.2.
I had an epiphany last nite and realized the reason I can't finds any codes was because I was looking in the wrong place because I thought it was an 8.2. I looked at where an 8.5 stamp would be (pass side axle - front). I ground it down nothing, but finally found it on the axle tube almost facing the ground it was so low. LLB233-1. Which means you are exactly correct, a 1971 Buick 2.73 open 8.5 built on the 233rd day 1st shift. It is a '71 and not a 72 because in 72 they dropped the "B" in the code. So, since it's not a numbers matching car I just got a beefier rear end! I'll put in an Eaton posi unit and should be good to go, thanks.
goatsnvairs is offline  
Sponsored Links
Advertisement
 
Reply

  Pontiac GTO Forum > The 1964-1974 Pontiac Tempest, Lemans & GTO > 1964-1974 Tempest, Lemans & GTO Undercarriage, Frame, Transmission and Differential Discussions.

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Pontiac GTO Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in











Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Similar Threads
Thread Thread Starter Forum Replies Last Post
GTO Rear End Identification help???? FireFox3434 1964-1974 Tempest, Lemans & GTO Undercarriage, Frame, Transmission and Differential Discussions. 14 03-21-2014 08:45 PM
Rear End Help Identification needed???? FireFox3434 1964-1974 Tempest, Lemans & GTO Exhaust, Suspension, Alignment, Fuel Tank and Brakes. 1 03-16-2014 03:54 PM
?- looking for new rear end gears and rear suspension whytedude422 Service, Maintenance and Technical Discussion 3 03-31-2010 04:11 AM
Rear axle identification??? ylwgto 1964-1974 Tempest, Lemans & GTO Undercarriage, Frame, Transmission and Differential Discussions. 6 11-06-2009 09:40 PM
Rear end identification help Jstreet 1964-1974 Tempest, Lemans & GTO Undercarriage, Frame, Transmission and Differential Discussions. 5 04-06-2009 10:17 PM

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome