12 Bolt GM ?
 

Have a 12 bolt rear under a 1970 Nova. Can any one tell if is correct for that year? Number on housing are 3894860nf = 1234567890 =A149.
54 1/2 flange to flange. 38948gonf
Thanks
Larry

Re: 12 Bolt GM ?
 

Larry-348690 is the casting number for a 12 bolt case but look on the top of the passenger side tube more towards the front of the car and there are a series of letters& numbers stamped in the tube---ya probably will hafta wire brush the tube clean to find those numbers---give me all of the numbers/letters and I can tell ya most of what ya want to know as far as WHAT IT WAS FROM THE FACTORY---now if the ratios have been changed or whatever cannot help ya there but what it was OEM yes--Comp

Re: 12 Bolt GM ?
 

The numbers on the tube is = 3894860nf
Thanks for your help.
Larry

Re: 12 Bolt GM ?
 

The numbers will be stamped in the front of the tube, not casting/raised numbers on the center section.
http://www.novaresource.org/axle.htm

Re: 12 Bolt GM ?
 

Number on tube is = BT0122G2 (E)
Thanks for your help.
Larry[/QUOTE]

Re: 12 Bolt GM ?
 

larry there will be a code something like
2 letters --then
4 numbers--then
2 or 3 letters


This is just an example but it will look something like this
QY 01 01 GE

Give me that code and I can tell ya what it was ORIGINALLY

Also any other numbers cast into the cast iron housing look along the ridges that is usually where they put them---that 3894860 is a 12 bolt cast iron center but without the other codes ya quite cannot tell what the housing is/was GM had different widths from model to model as well as year to year

Re: 12 Bolt GM ?
 

Doesn;t these numbers on the pass. side tube help ? BT 01 22 G2
E
Thanks
Larry

Re: 12 Bolt GM ?
 

larry the code ya gave me is what was in that rear originally when installed in the car
BT---3:55 posi
01---January
22---22nd day of the month
G----Detroit Gear & Axle
2----Night shift
E----Eaton Positraction Differential

Housing dimensions are
Center to center of the spring perches----42 3/4 inches
Inside of backing plate to inside of backing plate---53 1/4 inches
Outside of brake drum to outside of brake drum---60 1/4 inches

Re: 12 Bolt GM ?
 

Larry--I forgot to mention that that code is for a 68 or 69 rear end however see what the date code cast into the ribs on the left side of cast iron differential are ---also what is the serial number of your car you might have a very early 70 model and they had left over 69 housings to use up when they built your car

Re: 12 Bolt GM ?
 

i have a 12 bolt rearend #3894860nf on the tube #bm0213g2 there are also a279 con1 what rearend do i have.