GM rear end help

[enjenjo]

I am going to search, but one of you may have the info I need. I have a rear end here, which has a 10 bolt cover, but a 12 bolt carrier.  This is actually a BOP rear end, but this one came out of a 76 Malibu wagon, and was factory.

The problem I have is I want to change the gear ratio, but no new gears are available. This uses different pinion bearings than a normal 12 bolt.

I am trying to find out if the Hypoid offset on this gear set is the same as a regular 12 bolt  gear set. If it is, I can use a standard gearset with some juggling of bearings, and minor machine work on the carrier.

So any one know the Hypoid offset?

[kb426]

I'd like to help but you found something I've never seen.

[chimp koose]

I believe Hot Rod or Car Craft did an article on Dana ,9inch,and 12bolt diffs this month. I believe they stated the pinion offset in the article.

[enjenjo]

I believe Hot Rod or Car Craft did an article on Dana ,9inch,and 12bolt diffs this month. I believe they stated the pinion offset in the article.

Of course my sub ran out last month. I'll see if the news stand has it.

[wayne petty]

must be car craft...its not in the current hot rod....  my car craft ran out also... hr is good till sept. 2011...

just saw this

http://www.hotrod.com/techarticles/drivetrain/chevy_12_bolt_differential_install/index.html


this place seems to have a decent part page for rear ends... i have not found your bop 10 bolt with a 12 bolt carrier...

http://www.accuautoparts.com/axleinfo.jsp?sr=1

[tomslik]

i've heard of 'em but never seen one.
big GD help i am, right?  

[enjenjo]

Well, I found that the pinion offset is the same, but the gears can't be interchanged. The ring gear pilot diameter is different, that can be machined, or a spacer made depending on which way you are going. The ring gear bolts are a different size, but the same bolt pattern, that can be handled too. The killer is the pinion length. A regular 12 bolt pinion is 1/2" shorter, and there is no way to get the bearing and a yoke in the space available.

So we are starting over with another housing, we fitted the ring and pinion before we started on this one

I am amazed by the variations we are finding, I thought most of them were the same.