12 bolt rear end ratio help

67Poncho · Uber Guru

12 bolt rear end ratio help

Bago · Veteran Member

I'll be getting to this the weekend for sure! I was worried about grinding the number off!!

seventy2plus2 · Canadian Poncho Superstar!

Use a wire brush or wire wheel, you'll eventually find the numbers. They're stamped in, and as you saw they're easier to read with some chalk in them. In the absence of chalk, just we your finger and go over the metal above the stamping. You'll be able to read it.

67Poncho · Uber Guru

seventy2plus2 wrote:
Use a wire brush or wire wheel, you'll eventually find the numbers. They're stamped in, and as you saw they're easier to read with some chalk in them. In the absence of chalk, just we your finger and go over the metal above the stamping. You'll be able to read it.

Yes... I was going to suggest a medium rasp or finer file as well to remove the rust and scale... a grinder would be to aggressive...

North · Guru

soak a rag with CLR and let it hang on the area in question over night with a plastic grocery bag over it to keep it from drying. In the morning brush it with a floor brush before rinsing it.

Bago · Veteran Member

OK Right, found 'em, or whats left of 'em!

Right, the first two are 'DD' no doubt about that!

Second lot look to read 1124K, or they could rear 4124K. Last three are definitely 24K.

You'll be hard pushed to see it in my pics (below), and they are getting fainter the more I wire brush! So thats my lot.

I'll be interested to see what you all think!

www.flickr.com/photos/35630959@N07/31059738115/in/dateposted-public/

www.flickr.com/photos/35630959@N07/31023984476/in/dateposted-public/

www.flickr.com/photos/35630959@N07/30917417842/in/dateposted-public/

www.flickr.com/photos/35630959@N07/30917437532/in/dateposted-public/

Bago · Veteran Member

And yes, she is a 12 Bolt.

www.flickr.com/photos/35630959@N07/31060570185/in/dateposted-public/

67Poncho · Uber Guru

Good to hear... You can use a paint marker like I did and wipe off the surface excess... 3:31.... The chart I posted shows that it is an 8.875 ring gear...

Crap! Carl was snooty enough in last post calling out my math teacher but now he will have to expand all the door openings in his house because of his, "I told you so", swelled head...... ( biggrin biggrin biggrin biggrin biggrin )

-- Edited by 67Poncho on Thursday 17th of November 2016 01:04:05 PM

4SPEED427 · A Poncho Legend!

When we built our house we already put in the larger door frames....

3.31 makes sense with a 283 glide in a big car. I think a 3.07 would be pretty doggy away from a stop sign with a 2 speed in a car that's over 4000 pounds.

seventy2plus2 · Canadian Poncho Superstar!

DD = 3.31:1 open (non posi)

1124 = November 24

K = McKinnon Industries (plant code)

So the differential was assembled November 24, 1966. From that, I'd presume your car was assembled in December 1966 or January 1967.

Bago · Veteran Member

December 66, you are correct. Now, the reason I need the ratio is because I'm currently about to build a 454 big block for this car. However, I want to fit a comp cams Thumpr cam and for this they need to know the diff ratio and stall speed. I have a th400 box to go in, anyone know how to determine the stall speed?

67Poncho · Uber Guru

Carl Stevenson wrote:
When we built our house we already put in the larger door frames....

3.31 makes sense with a 283 glide in a big car. I think a 3.07 would be pretty doggy away from a stop sign with a 2 speed in a car that's over 4000 pounds.

That's odd to hear.... I pulled a posi from a '69 Parisienne with a 6cyl and a 'Glide and it had a 3:07.... and my '70 with a 6cyl and a THM350 had a 3:07... I swapped complete axles in lieu of the posi.... Maybe that changed in '69-ish...

66 Beau · Poncho Master!

If the car is running, you could try putting it in gear, foot firmly on the brake, and read the tach as you give her gas. I'm not sure how accurate this method is, but I've used it to get an idea of the stall speed. I don't know if you can tell by looking at the converter. Stall speed is determined by the size, shape, angle of the fins inside. I don't recall seeing any sort of markings on the outside of the torque converters, but maybe the make/model is stamped on it somewhere?

As for 3.07 rear ends with 6 cylinder engines, I wonder if this is due to the low end torque these engines produce?

4SPEED427 · A Poncho Legend!

Somewhere I think I have the powertrain chart for 66. If I can find it I will post it.

It does sound like the thinking from 66-69 changed.

12 bolt 6 cylinder Powerglide eh? You gotta love Canadian cars. We just don't hear of US models having this kind of setup but it seems to be common in Beaumonts and B bodies here.