Looking 1966 C2 diff cover and a date code question
Thread Starter
Racer
Joined: Dec 2013
Posts: 418
Likes: 32
From: Ct
Looking 1966 C2 diff cover and a date code question
My car is away in a shop. Can someone tell me where the code is on the diff that has the gear and assembly date code?
I believe mine once said FA 4 1 66
Is the number above on the cover or the diff housing itself?
I am looking for a replacement cover for this 1966 April 7th production date 3.70 390 BB car.
The NCRS manual says it is supposed to have a part number 3871375.
Thank you,
Dennis
I believe mine once said FA 4 1 66
Is the number above on the cover or the diff housing itself?
I am looking for a replacement cover for this 1966 April 7th production date 3.70 390 BB car.
The NCRS manual says it is supposed to have a part number 3871375.
Thank you,
Dennis
Team Owner
Joined: Oct 2000
Posts: 38,897
Likes: 1,926
From: Washington Michigan
My car is away in a shop. Can someone tell me where the code is on the diff that has the gear and assembly date code?
I believe mine once said FA 4 1 66
Is the number above on the cover or the diff housing itself?
I am looking for a replacement cover for this 1966 April 7th production date 3.70 390 BB car.
The NCRS manual says it is supposed to have a part number 3871375.
Thank you,
Dennis
I believe mine once said FA 4 1 66
Is the number above on the cover or the diff housing itself?
I am looking for a replacement cover for this 1966 April 7th production date 3.70 390 BB car.
The NCRS manual says it is supposed to have a part number 3871375.
Thank you,
Dennis
Thread Starter
Racer
Joined: Dec 2013
Posts: 418
Likes: 32
From: Ct
Racer
Joined: May 2017
Posts: 293
Likes: 74
While we're on this subject, I've always wondered what can be surmised by the number on the rear differential. I did the old rotate the wheel and count the drive shaft rotations and believe I've got a 3.35 ratio. The number that's on the differential is 3830303. Does that suggest something else?
Rick
Rick
Race Director
Joined: Apr 2005
Posts: 11,277
Likes: 2,139
From: Bowling Green, Kentucky
While we're on this subject, I've always wondered what can be surmised by the number on the rear differential. I did the old rotate the wheel and count the drive shaft rotations and believe I've got a 3.35 ratio. The number that's on the differential is 3830303. Does that suggest something else?
Rick
Rick
That sounds like the casting/part number for the differential case. Your ratio is likely 3.36 and this is shown by the first two letters stamped into the rear carrier cover. From JohnZ pic these numbers are "AM". For a 1967 car (which this is) AM = 3.36 posi-traction for a small block engine.
Larry
Racer
Joined: May 2017
Posts: 293
Likes: 74
Rick:
That sounds like the casting/part number for the differential case. Your ratio is likely 3.36 and this is shown by the first two letters stamped into the rear carrier cover. From JohnZ pic these numbers are "AM". For a 1967 car (which this is) AM = 3.36 posi-traction for a small block engine.
Larry
That sounds like the casting/part number for the differential case. Your ratio is likely 3.36 and this is shown by the first two letters stamped into the rear carrier cover. From JohnZ pic these numbers are "AM". For a 1967 car (which this is) AM = 3.36 posi-traction for a small block engine.
Larry
Race Director
Joined: Apr 2005
Posts: 11,277
Likes: 2,139
From: Bowling Green, Kentucky
GM3 is a mold or pattern number for the mold used for casting your differential case or cover. I can't tell you whether case or cover without a pic.
Larry
Last edited by Powershift; Jun 8, 2019 at 03:04 PM.
Racer
Joined: May 2017
Posts: 293
Likes: 74
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Race Director
Joined: Apr 2005
Posts: 11,277
Likes: 2,139
From: Bowling Green, Kentucky
CA = 3.36 std axle
CB = 3.36 posi
CC = 3.55 posi
CD = 3.70 posi
CE = 4.11 posi
CF = 4.56 posi
CJ = 3.08 posi
CZ = 3.08 std axle
CX = 3.70 std axle
That's all there is.............
Pick one. Based on what you said earlier, CB is the likely choice. Count driveshaft revs again for one tire rev. If both wheels move together it is a posi.
Larry
EDIT: The 2 9 64 is February 9, 1964. This is the day your differential was made.
CB = 3.36 posi
CC = 3.55 posi
CD = 3.70 posi
CE = 4.11 posi
CF = 4.56 posi
CJ = 3.08 posi
CZ = 3.08 std axle
CX = 3.70 std axle
That's all there is.............
Pick one. Based on what you said earlier, CB is the likely choice. Count driveshaft revs again for one tire rev. If both wheels move together it is a posi.
Larry
EDIT: The 2 9 64 is February 9, 1964. This is the day your differential was made.
Last edited by Powershift; Jun 8, 2019 at 06:19 PM.