Fun with decoding GM stamps
Thread Starter
Team Owner
Joined: Oct 2004
Posts: 23,831
Likes: 10
From: Springfield MO
St. Jude Donor '07
Fun with decoding GM stamps
Finally got the "dirt collection" shield off of my differential and wire-brushed the bottom of it. The case is stamped as follows:
OA = 3.08 gearing (but it acts like it has at least 3.55s, and the tach agrees...this will require further investigation, as it doesn't look like it's ever been removed)
229 = Monday, 16 Aug 1976 (this jives with the Thursday, 2 Sep. 1976 build date)
W = no idea
7E = no idea
1 = no idea
Does anyone know what the last four characters represent? There are spaces betwen the W and 7 and the E and 1, but not as far as the gaps between the A and 2 and 9 and W.
OA = 3.08 gearing (but it acts like it has at least 3.55s, and the tach agrees...this will require further investigation, as it doesn't look like it's ever been removed)
229 = Monday, 16 Aug 1976 (this jives with the Thursday, 2 Sep. 1976 build date)
W = no idea
7E = no idea
1 = no idea
Does anyone know what the last four characters represent? There are spaces betwen the W and 7 and the E and 1, but not as far as the gaps between the A and 2 and 9 and W.
Le Mans Master
Joined: Sep 2002
Posts: 5,236
Likes: 898
From: Myrtle Beach SC
Originally Posted by I'm Batman
Finally got the "dirt collection" shield off of my differential and wire-brushed the bottom of it. The case is stamped as follows:
OA = 3.08 gearing (but it acts like it has at least 3.55s, and the tach agrees...this will require further investigation, as it doesn't look like it's ever been removed)
229 = Monday, 16 Aug 1976 (this jives with the Thursday, 2 Sep. 1976 build date)
W = no idea
7E = no idea
1 = no idea
Does anyone know what the last four characters represent? There are spaces betwen the W and 7 and the E and 1, but not as far as the gaps between the A and 2 and 9 and W.
OA = 3.08 gearing (but it acts like it has at least 3.55s, and the tach agrees...this will require further investigation, as it doesn't look like it's ever been removed)
229 = Monday, 16 Aug 1976 (this jives with the Thursday, 2 Sep. 1976 build date)
W = no idea
7E = no idea
1 = no idea
Does anyone know what the last four characters represent? There are spaces betwen the W and 7 and the E and 1, but not as far as the gaps between the A and 2 and 9 and W.
W is the code for the Warren Michigan Plant
the 229 is a Julian date.
E indicates the posi-traction source of Eaton and the 1 is the shift that assembled the unit. The 7 suggests a 77 production date but I believe that's based on calender year which is inconsistent with you build date. But I may be missing something here.
Racer
Joined: Dec 2004
Posts: 379
Likes: 0
From: Fairfield Texas
I dont think the year of manufacture is represented in the stamped
in code on the bottom of case. There is a date code cast into the
differential case. Should be one letter "A" for Jan. etc. followed by
one or two numbers for day of month and one more number for year.
The stamped in code should begin with 2 letters for ratio, one letter
for assenbly plant,then one two or three numbers for day of year
assembled,one letter for source of posi.,one number for shift that
assembled the unit.
in code on the bottom of case. There is a date code cast into the
differential case. Should be one letter "A" for Jan. etc. followed by
one or two numbers for day of month and one more number for year.
The stamped in code should begin with 2 letters for ratio, one letter
for assenbly plant,then one two or three numbers for day of year
assembled,one letter for source of posi.,one number for shift that
assembled the unit.
Thread Starter
Team Owner
Joined: Oct 2004
Posts: 23,831
Likes: 10
From: Springfield MO
St. Jude Donor '07
The 229 is a Julian date, which I looked up - it was made in mid-August 1976, which would match the build date of Sept 2, 1976. The car is a very early 77 model, around #2500.
OA 229 W 7E 1
OA 229 W 7E 1
Racer
Joined: Dec 2004
Posts: 379
Likes: 0
From: Fairfield Texas
Originally Posted by I'm Batman
The 229 is a Julian date, which I looked up - it was made in mid-August 1976, which would match the build date of Sept 2, 1976. The car is a very early 77 model, around #2500.
OA 229 W 7E 1
OA 229 W 7E 1
of case should read OA W 229 E 1. I dont know what the 7 is there
for and dont know why the other numbers are not in the order they
are supposed to be in . Maybe the fellow that stamped that puppy
was having a bad day.
Drifting
Joined: Oct 2003
Posts: 1,426
Likes: 1
From: VetteMOD
St. Jude Donor '05-'07
Originally Posted by chevylit
According to My resto. book the above number You found on bottom
of case should read OA W 229 E 1. I dont know what the 7 is there
for and dont know why the other numbers are not in the order they
are supposed to be in . Maybe the fellow that stamped that puppy
was having a bad day.
of case should read OA W 229 E 1. I dont know what the 7 is there
for and dont know why the other numbers are not in the order they
are supposed to be in . Maybe the fellow that stamped that puppy
was having a bad day.
Racer
Joined: Dec 2004
Posts: 379
Likes: 0
From: Fairfield Texas
I cant even tell what thats SUPPOSED to be. I wonder why these
stampings are so screwed up? Also wonder why both rearends have
that 7 in the sequence. Maybe a different resto. book than the one I
have would have the answer.
stampings are so screwed up? Also wonder why both rearends have
that 7 in the sequence. Maybe a different resto. book than the one I
have would have the answer.
Drifting
Joined: Oct 2003
Posts: 1,426
Likes: 1
From: VetteMOD
St. Jude Donor '05-'07
Originally Posted by chevylit
I cant even tell what thats SUPPOSED to be. I wonder why these
stampings are so screwed up? Also wonder why both rearends have
that 7 in the sequence. Maybe a different resto. book than the one I
have would have the answer.
stampings are so screwed up? Also wonder why both rearends have
that 7 in the sequence. Maybe a different resto. book than the one I
have would have the answer.
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Thread Starter
Team Owner
Joined: Oct 2004
Posts: 23,831
Likes: 10
From: Springfield MO
St. Jude Donor '07
Originally Posted by BBShark
I think the fellow that stamped it may have a drinking and/or vision problems. I think he may be the guy who stamped this rear 23 days later!
Le Mans Master
Joined: Sep 2002
Posts: 5,236
Likes: 898
From: Myrtle Beach SC
Originally Posted by chevylit
I cant even tell what thats SUPPOSED to be. I wonder why thesestampings are so screwed up? Also wonder why both rearends havethat 7 in the sequence. Maybe a different resto. book than the one I have would have the answer.
Early used a 1 AX 12 28 68 W format
Mid years used AX W 315 X 2
Late used OK 311 W 7E 1 format
So the stamping aren't screwed up...just different
