differential question

[Stephen B.]

Good evening. I have a 72 coupe and trying to get information on the third member which I know has been out for some reason in the past. The casting numbers are as follows...GM 9. CON 5 and 38991483. Is this a 72 third member? I know for sure it's a 3:08. Thanks for help here.

[Joe L.]

Re: differential question

Good evening. I have a 72 coupe and trying to get information on the third member which I know has been out for some reason in the past. The casting numbers are as follows...GM 9. CON 5 and 38991483. Is this a 72 third member? I know for sure it's a 3:08. Thanks for help here.

Stephen-------

From the information you've provided, there's no way to tell if it's a 1972 rear end. You need to find the stamped-in series of alpha characters and numbers located on the bottom of the main case, just forward of where the cover attaches.
S

[Stephen B.]

Re: differential question

Thank you Joe

[Stephen B.]

Re: differential question

Joe, check the location you recommended an found this AWw069 E1, so I take it, I have a 69 third member?

[Terry M.]

Re: differential question

Joe, check the location you recommended an found this AWw069 E1, so I take it, I have a 69 third member?

Stephen

AW = 3.08:1 ratio was originally installed in that differential case. The E1 means the internal components were assembled by Eaton on the first shift.
069 means it was assembled on the 69th day of the year or March 10 or March 9th if it was a Leap Year. The problem is without the date code (near the fill plug) there is no way to tell what year that differential was assembled. I can tell you it is a 1971 or later because the Julian Dating (the 069 date code) didn't begin until 1971. If the March dates fit with the build date of your car (stamping on the upper right hand of your Trim Tag) there is a chance the case is original to your car.

[Gary R.]

Re: differential question

Since the diff has been worked on in the past who knows what is left of the original parts. There is a casting date on the lower left side- below the axle to the bottom. That would give you a better idea of what you have but in the case of a "9" it could be a 69 or 79. The bearing caps are different between those years so if you were to pull the cover and take pictures we can tell you what you have. Also the Ring Gear will have a date code on it.

[Stephen B.]

Re: differential question

Gary, thank you the information and I will check to see what I can find. I did have some issues I found taken this apart as stated to Terry, but this car is going back together correctly this time. This car has been off the road for over 15 years and I have the 2 build sheets, so far the numbers match,but its a strange one.

[Stephen B.]

Re: differential question

Terry, thank you so much for the information. I will check for date as you suggested and see what I can find. I did find wrong and missing hardware when I took the car apart, so I know this area has been apart before and some people just throw things back together to get it done. The car is going back together Right with the RIGHT parts and installed RIGHT by me. This car has been of the road for over 15 years, but I did find 2 build sheets, but it's a strange one. Heck, I can't find the dealer or zone either can NCRS.....oh well

[Terry M.]

Re: differential question

Terry, thank you so much for the information. I will check for date as you suggested and see what I can find. I did find wrong and missing hardware when I took the car apart, so I know this area has been apart before and some people just throw things back together to get it done. The car is going back together Right with the RIGHT parts and installed RIGHT by me. This car has been of the road for over 15 years, but I did find 2 build sheets, but it's a strange one. Heck, I can't find the dealer or zone either can NCRS.....oh well

Gary R. has the location of the date more accurately than I do. He has seen more of these differentials than I ever will.

NCRS doesn't have the date, dealer or zone for my 1970, not that I need them since I picked up the car myself. Some of the micro-fish they work off of has some damage.

[Gary R.]

Re: differential question

Here is the date code on a diff




Here is the stamping, which would be 1-2 months after the date code but that varied.



65-70 bearing caps look like this one- no cast in tab.



71-79 have the tab


63-64 caps were wider and had a tab

[Terry M.]

Re: differential question

Here is the date code on a diff




Here is the stamping, which would be 1-2 months after the date code but that varied.



65-70 bearing caps look like this one- no cast in tab.



71-79 have the tab

63-64 caps were wider and had a tab

Gary
You are amazing, and so kind. Nice going

[Stephen B.]

Re: differential question

Terry, thank you again this information. The casting number by the filler plug looks like 8 (?) 232. Again, thank you.

[Terry M.]

Re: differential question

Terry, thank you again this information. The casting number by the filler plug looks like 8 (?) 232. Again, thank you.

Could it be: B232 That would be February 23, 1972. Does that fit with the build date of your car? It does fit with the March 10 assembly date stamped on the bottom of the case.

[Gary R.]

Re: differential question

The fill plug is in the cover, that would be the cover date code, not the housing. Since the diff has been apart it could have another cover or the diff could have been replaced and the org cover kept.

[Stephen B.]

Re: differential question

Terry, thank you for all your help.