Differential in Catalina

chromebumpers

chromebumpers

solid fixture here in the forum
Staff member
Here is some photos and numbersb


#1235198 there is an "N" on top of those numbers On the left it says C131
aug5%20009.jpg


Below - hard to read these numbers 07680? on the top left 12945 ? again, hard to read
aug5%20011.jpg
 
http://wallaceracing.com/axledata2.htm

http://tech.oldsgmail.com/axle_useage.php

http://www.oldsmobility.com/old/10bolt-tech.htm

http://chevellestuff.net/qd/rear_axle_info.htm

http://www.differentials.com/technical-help/differential-identification

http://www.differentials.com/gm-axle-ratio-identification-codes

http://www.differentials.com/technical-help/differential-identification

http://www.fourwheeler.com/how-to/transmission-drivetrain/1312-10-bolt-builder-s-guide/

differ1.jpg

differ2.jpg

differ3.jpg

med_1496184503-1495541036-GM_Rear_End_ID.jpg

differ4.png
differ5.png

differ6.png

differ7.png


med_1496184503-1495541036-GM_Rear_End_ID.jpg

axlecode.gif


1974AGaxles.jpg


The axle code, which is a two-character code, is stamped on the front passenger side axle tube to the left of the carrier case. For example, axle code PX G70621 found on a 1977 Trans Am would be deciphered as; PX = Ring and Pinion Gear size 3.23(shown below), G = Manufacturer, Chevrolet Gear and Axle, 062 = Julian date which is the 62nd day of 1977 or March 1, 1977, 1= is the shift when built, in this case 1st shift.

1967
UN - 2.56 Rear Gear (Posi)
UP - 2.78 Rear Gear (Posi)
UR - 2.93 Rear Gear (Posi)
US - 3.08 Rear Gear (Posi)
UT - 3.23 Rear Gear (Posi)
UV - 3.36 Rear Gear (Posi)
UW - 3.55 Rear Gear (Posi)
UX - 3.90 Rear Gear (Posi)
UY - 4.33 Rear Gear (Posi)
XB - 2.56 Rear Gear (Open)
XC - 2.78 Rear Gear (Open)
XD - 2.93 Rear Gear (Open)
XE - 3.08 Rear Gear (Open)
XF - 3.23 Rear Gear (Open)
XG - 3.36 Rear Gear (Open)
XH - 3.55 Rear Gear (Open)



1968
UN - 2.56 Rear Gear (Posi)
UP - 2.78 Rear Gear (Posi)
UR - 2.93 Rear Gear (Posi)
US - 3.08 Rear Gear (Posi)
UT - 3.23 Rear Gear (Posi)
UV - 3.36 Rear Gear (Posi)
UW - 3.55 Rear Gear (Posi)
UX - 3.90 Rear Gear (Posi)
UY - 4.33 Rear Gear (Posi)
XB - 2.56 Rear Gear (Open)
XC - 2.78 Rear Gear (Open)
XD - 2.93 Rear Gear (Open)
XE - 3.08 Rear Gear (Open)
XF - 3.23 Rear Gear (Open)
XG - 3.36 Rear Gear (Open)
XH - 3.55 Rear Gear (Open)



1969
ZB - 2.56 Rear Gear (Posi)
ZC - 2.78 Rear Gear (Posi)
ZD - 2.93 Rear Gear (Posi)
ZE - 3.08 Rear Gear (Posi)
ZF - 3.23 Rear Gear (Posi)
ZG - 3.36 Rear Gear (Posi)
ZH - 3.55 Rear Gear (Posi)
ZK - 3.90 Rear Gear (Posi)
ZM - 4.33 Rear Gear (Posi)
YB - 2.56 Rear Gear (Open)
YC - 2.78 Rear Gear (Open)
YD - 2.93 Rear Gear (Open)
YE - 3.08 Rear Gear (Open)
YF - 3.23 Rear Gear (Open)
YG - 3.36 Rear Gear (Open)
YH - 3.55 Rear Gear (Open)
1970
COF - 3.08 Rear Gear (Posi)
COL - 3.36 Rear Gear (Posi)
COT - 3.07 Rear Gear (Posi)
COV - 3.31 Rear Gear (Posi)
COX - 3.55 Rear Gear (Posi)
COZ - 3.73 Rear Gear (Posi)
CRY - 2.73 Rear Gear (Posi)
COE - 3.08 Rear Gear (Open)
COK - 3.36 Rear Gear (Open)
COS - 3.07 Rear Gear (Open)
COU - 3.31 Rear Gear (Open)
COW - 3.55 Rear Gear (Open)
CRX - 2.73 Rear Gear (Open)



1971
CA - 2.73 Rear Gear (Posi)
CB - 4.10 Rear Gear (Posi)
CG - 3.73 Rear Gear (Posi)
CJ - 3.42 Rear Gear (Posi)
GY - 3.08 Rear Gear (Posi)
CK - 3.42 Rear Gear (Open)
GX - 3.08 Rear Gear (Open)
GZ - 2.73 Rear Gear (Open) 1972
CA - 2.73 Rear Gear (Posi)
CG - 3.73 Rear Gear (Posi)
CJ - 3.42 Rear Gear (Posi)
CM - 3.42 Rear Gear (Posi)
GY - 3.08 Rear Gear (Posi)
CK - 3.42 Rear Gear (Open)
CL - 3.42 Rear Gear (Open)
GX - 3.08 Rear Gear (Open)
GZ - 2.73 Rear Gear (Open)
1973
CA - 2.73 Rear Gear (Posi)
CM - 3.42 Rear Gear (Posi)
GY - 3.08 Rear Gear (Posi)
CL - 3.42 Rear Gear (Open)
GX - 3.08 Rear Gear (Open)
GZ - 2.73 Rear Gear (Open)



1974
CA - 2.73 Rear Gear (Posi)
CM - 3.42 Rear Gear (Posi)
GY - 3.08 Rear Gear (Posi)
CL - 3.42 Rear Gear (Open)
GX - 3.08 Rear Gear (Open)
GZ - 2.73 Rear Gear (Open) 1975
PT - 2.56 Rear Gear (Posi)
PU - 2.73 Rear Gear (Posi)
PW - 3.08 Rear Gear (Posi)
PA - 2.73 Rear Gear (Open)
PC - 3.08 Rear Gear (Open)
PG - 2.56 Rear Gear (Open)
1976
PS - 2.41 Rear Gear (Posi)
PU - 2.73 Rear Gear (Posi)
PW - 3.08 Rear Gear (Posi)
PX - 3.23 Rear Gear (Posi)
LD - 3.23 Rear Gear (Posi)
PA - 2.73 Rear Gear (Open)
PC - 3.08 Rear Gear (Open)
PJ - 2.41 Rear Gear (Open)
PD - 3.23 Rear Gear (Open) 1977
PS - 2.41 Rear Gear (Posi)
PT - 2.56 Rear Gear (Posi)
PW - 3.08 Rear Gear (Posi)
PX - 3.23 Rear Gear (Posi)
PJ - 2.41 Rear Gear (Open)
PC - 3.08 Rear Gear (Open)
PH - 2.56 Rear Gear (Open)
PD - 3.23 Rear Gear (Open)
1978
PS - 2.41 Rear Gear (Posi)
PT - 2.56 Rear Gear (Posi)
PW - 3.08 Rear Gear (Posi)
PX - 3.23 Rear Gear (Posi)
PP - 3.23 Rear Gear (Posi)
PJ - 2.41 Rear Gear (Open)
PH - 2.56 Rear Gear (Open)
PC - 3.08 Rear Gear (Open)
PD - 3.23 Rear Gear (Open)
PM - 3.23 Rear Gear (Open)



1979
PS - 2.41 Rear Gear (Posi)
PV - 2.41 Rear Gear (Posi)
PT - 2.56 Rear Gear (Posi)
PU - 2.73 Rear Gear (Posi)
PR - 2.73 Rear Gear (Posi)
PW - 3.08 Rear Gear (Posi)
PQ - 3.08 Rear Gear (Posi)
PX - 3.23 Rear Gear (Posi)
PP - 3.23 Rear Gear (Posi)
PO - 3.42 Rear Gear (Posi)
PJ - 2.41 Rear Gear (Open)
PH - 2.56 Rear Gear (Open)
PA - 2.73 Rear Gear (Open)
PC - 3.08 Rear Gear (Open)
PD - 3.23 Rear Gear (Open) 1980
PS - 2.41 Rear Gear (Posi)
PV - 2.41 Rear Gear (Posi)
PT - 2.56 Rear Gear (Posi)
PU - 2.73 Rear Gear (Posi)
PO - 3.08 Rear Gear (Posi)
PW - 3.08 Rear Gear (Posi)
PQ - 3.08 Rear Gear (Posi)
PX - 3.23 Rear Gear (Posi)
PY - 3.42 Rear Gear (Posi)
PO - 3.42 Rear Gear (Posi)
PJ - 2.41 Rear Gear (Open)
PH - 2.56 Rear Gear (Open)
PA - 2.73 Rear Gear (Open)
PD - 3.23 Rear Gear (Open)
PB - 3.42 Rear Gear (Open)
PC - 3.08 Rear Gear (Open) 1981
PS - 2.41 Rear Gear (Posi)
PV - 2.41 Rear Gear (Posi)
PT - 2.56 Rear Gear (Posi)
PU - 2.73 Rear Gear (Posi)
PQ - 3.08 Rear Gear (Posi)
PW - 3.08 Rear Gear (Posi)
PY - 3.42 Rear Gear (Posi)
PX - 3.23 Rear Gear (Posi)
PJ - 2.41 Rear Gear (Open)
PH - 2.56 Rear Gear (Open)
PA - 2.73 Rear Gear (Open)
PC - 3.08 Rear Gear (Open)
PD - 3.23 Rear Gear (Open)

https://www.thepartsplaceinc.com/data-sheets/Pontiac Rear End Decoder.pdf
 
Last edited:
I didn't see any numbers on the axle tube where the diagram shows them. Do the numbers on the differential webs mean anything? Do these cars all come with positraction?
 
I was pleasantly surprised everything is solid and without any rust. There's really old under coating that likely saved everything floors are nice under the carpet too. The frame is clean and without any patch welding.
 
Its Supposed to be a Special 1968-70 Catalina "B" Car Pontiac 8.2" Rear Diff.

Its been replaced with a 1971-77 G Body Grand Prix 8.5" Differential I believe .
 
The 1965-67 2+2 Catalina had a very special Rear Diff.
Used in 1965-67 Grand Prix too.
 
Spin a rear tire, do a small burnout, or pop the rear diff cover off.
Find out if its a Posi rear or not.
 
The stamped letters and numbers are 99-100 times gone rusted off.
Only see them on Mint Clean rear diffs.
Glass beading sand blasting wipes stampings off too.

They are stamped Deep and hard on 1957-64 Pontiac 9.3 Rears.
Dana 60 Too.
 
Ok, so I did manage to find a number on the pass side axle tube

NK G0812 1

Does that indicate what it is?
 
The Classic GM 10-BOLT 8.5- 8-1/2 Rear Iron Ears are present.
Located at 5 & 7 O'Clock.

The ears are not used on 1964-1970 Pontiac 8.2" 10-bolt Rears.
 
chromebumpers said:
So the axle ratio code is "NK" ?
Click to expand...
Grumpy is unable to find all Pontiac Info & Codes because it has never been put on the internet.
High Perfomance Pontiac Magazine is now defunct gone since 2014.
Internet postings older than 2005 near impossible to find or not there period.
Its in old magazines & factory literature that I have & others.
Most I have memorized if I read it prior.
If I did not read it then Its not in my memory.
NK means Notta to me.
Have to research more later for you Richard.
 
I picked up another old Pontiac Book recent.
Documented Pontiac was experimenting with 3" - 3-1/2"- & 3-7/8" Exhaust outlet Manifold Headers.
Very Kool.
I won that ebay auction too.
 
The the axle ID clearly begins with "N K"(Looking from the U-joint side, it's on the left axle tube).

Is there more than one color blue, or blue-Aqua for the motor? I see several different variations and I'd like to know which one is correct. There was an engine done that had a sort of "pearl" hue to the silver-blue that looked great, but I bet it wasn't correct. I think if I found it I would use it any way!
 
chromebumpers said:
The the axle ID clearly begins with "N K"(Looking from the U-joint side, it's on the left axle tube).

Is there more than one color blue, or blue-Aqua for the motor? I see several different variations and I'd like to know which one is correct. There was an engine done that had a sort of "pearl" hue to the silver-blue that looked great, but I bet it wasn't correct. I think if I found it I would use it any way!
Click to expand...
The Pearl Hue Is 1966-1970 Pontiac Silver Metallic Blue.
Its real hard to duplicate correct.
I have it custom mixed and Spray with a gun and compressor.
Secret is there are 7 colors mixed together to duplicate right.

Bill Hersh paint in Hemmings Ads prettt good I hear. Haven't used myself .
 
87vette81big said:
I picked up another old Pontiac Book recent.
Documented Pontiac was experimenting with 3" - 3-1/2"- & 3-7/8" Exhaust outlet Manifold Headers.
Very Kool.
I won that ebay auction too.
Click to expand...

I had a great Coffee table book on Pontiacs. It was co-written by the people that are behind PHS. I never saw another one and I loaned it out to Mark Mecum at Palm Beach and that was the last time I saw it.

The Catalina's exhaust looks very choked. It's tapered down at the manifold connection at 2" and it's squeezed in on every little bend. That's why I need to change it.
 
Ok Not Driving again Richard.
Easier to post from my phone now.

To answer about Pontiac Safety Track Posi Traction.
The only Pontiacs to have it stock Guaranteed is the 1969-81 Trans Am.
All of them. Its standard part of the T/A package.
And the 1969- 1970 GTO Ram Air IV -4 400.
Optional extra cost in all Pontiacs.
Historically people did not believe in Posi Traction.
Don't know why but that's how they thought in 1960's.
 
chromebumpers said:
I had a great Coffee table book on Pontiacs. It was co-written by the people that are behind PHS. I never saw another one and I loaned it out to Mark Mecum at Palm Beach and that was the last time I saw it.

The Catalina's exhaust looks very choked. It's tapered down at the manifold connection at 2" and it's squeezed in on every little bend. That's why I need to change it.
Click to expand...
Everything Pontiac Did had a purpose.
Only the Big Block Chevrolet has similar Class.
SBC Stock Factory was a cluster Fick.
 
chromebumpers said:
I had a great Coffee table book on Pontiacs. It was co-written by the people that are behind PHS. I never saw another one and I loaned it out to Mark Mecum at Palm Beach and that was the last time I saw it.

The Catalina's exhaust looks very choked. It's tapered down at the manifold connection at 2" and it's squeezed in on every little bend. That's why I need to change it.
Click to expand...
I loaned out A GTO Facts book 15 -20 years ago and never saw it again too.
Been searching Fleabay for it.
Was a Great Book.
Other Guy must have thought likewise .
 
image.jpg I managed to capture the ID numbers on the pass side axle tube. I can expand the photo and see it well. However - where can I get a complete listing of codes?
 
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