63 Corvette rear differential

[Bob R.]

I have a 63 corvette and was trying to figure out the rear end ratio of my car. Someone told me I could rotate the rear wheels and count the revolutions of the drive shaft. It would seem difficult to tell the exact ratio that way. Does anyone know how to interpret the numbers on the rear case?
Thanks Bob R

[Joe L.]

Re: 63 Corvette rear differential

Bob-----

The differential code will be found stamped into the bottom of the case just forward of where the cover mates with it. Codes are as follows:

CA= 3.36:1 non-posi

CB= 3.36:1 posi

CC= 3.55:1 posi

CD= 3.70:1 posi

CE= 4.11:1 posi

CF= 4.56:1 posi

CJ= 3.08:1 posi

CX= 3.70:1 non-posi

CZ= 3.08:1 non-posi

The above codes only "work" if the differential unit is original and the contents thereof are unchanged over the years.

[Joe L.]

Re: 63 Corvette rear differential

Bob-----

The differential code will be found stamped into the bottom of the case just forward of where the cover mates with it. Codes are as follows:

CA= 3.36:1 non-posi

CB= 3.36:1 posi

CC= 3.55:1 posi

CD= 3.70:1 posi

CE= 4.11:1 posi

CF= 4.56:1 posi

CJ= 3.08:1 posi

CX= 3.70:1 non-posi

CZ= 3.08:1 non-posi

The above codes only "work" if the differential unit is original and the contents thereof are unchanged over the years.

[Stephen G.]

Re: 63 Corvette rear differential

Joe;

Can this code be seen with the rear end still in the car ? I'm not sure exactly where you mean. I'm looking for my info as well.

[Stephen G.]

Re: 63 Corvette rear differential

Joe;

Can this code be seen with the rear end still in the car ? I'm not sure exactly where you mean. I'm looking for my info as well.

[Joe L.]

Re: 63 Corvette rear differential

Stephen-----

Yes, it can easily be seen with the differential unit in the car. It's stamped right on the bottom of the housing and is usually not obscured by anything. However, it is often very lightly stamped so you may have to wire brush the area if rust or paint are present.

[Joe L.]

Re: 63 Corvette rear differential

Stephen-----

Yes, it can easily be seen with the differential unit in the car. It's stamped right on the bottom of the housing and is usually not obscured by anything. However, it is often very lightly stamped so you may have to wire brush the area if rust or paint are present.

[Wayne K.]

Re: 63 Corvette rear differential

I wanted to verify the gear ratio as stamped on my differential so I raised both rear tires and marked the driveshaft and tire and one circumference of the tire resulted in approximately 3 3/4 turns of the driveshaft, thus 3:70 which is the code stamped on the differential. Without taking it apart I think this is the easiest way to find out what you really have in the differential.

[Wayne K.]

Re: 63 Corvette rear differential

I wanted to verify the gear ratio as stamped on my differential so I raised both rear tires and marked the driveshaft and tire and one circumference of the tire resulted in approximately 3 3/4 turns of the driveshaft, thus 3:70 which is the code stamped on the differential. Without taking it apart I think this is the easiest way to find out what you really have in the differential.

[Stephen G.]

Re: 63 Corvette rear differential

Joe;

I finally found the markings: CE 1 7 63. Looks like I actually have at least ONE original part on my 63 ! However the rear casting is marked 3871975 and I can't find anything on the CD, printed or in archives that gets a hit on that number.

Steve

[Stephen G.]

Re: 63 Corvette rear differential

Joe;

I finally found the markings: CE 1 7 63. Looks like I actually have at least ONE original part on my 63 ! However the rear casting is marked 3871975 and I can't find anything on the CD, printed or in archives that gets a hit on that number.

Steve

[Joe L.]

Re: 63 Corvette rear differential

Steve----

GM #3871975 is the casting number for the GM PART #3871974 rear cover. This cover was used in PRODUCTION from about 1965 through about 1975. It was also the SERVICE cover for all 63-75 applications from about 1965 until it was discontinued. So, at some time, your original cover was replaced by a SERVICE cover (or a used cover from a 65-75 model Corvette).

[Joe L.]

Re: 63 Corvette rear differential

Steve----

GM #3871975 is the casting number for the GM PART #3871974 rear cover. This cover was used in PRODUCTION from about 1965 through about 1975. It was also the SERVICE cover for all 63-75 applications from about 1965 until it was discontinued. So, at some time, your original cover was replaced by a SERVICE cover (or a used cover from a 65-75 model Corvette).