1968 Differtial code

[Keith T.]

Can someone please decode this differential number for me.

2AV5368S

I have a 327 engine and a TH400 Automatic Trans.

Would this be the correct differential for this car? It appears to have never been replaced, as it has the original shocks.......believe it or not.

Thanks,

KT

[Jim T.]

Re: 1968 Differtial code

Kieth the NCRS Spec Guide for 68-69 shows AV ratio is a 3:08 with optional positraction. 1970 and later C3's positraction was standard.

[Peter M.]

Re: 1968 Differtial code

3:08 Positraction built on May 3, 1968. See the 1968 Corvette differential codes attached:

1968 C3 Differentials were manufactured at Warren and are suffixed 'W'. The HD side yokes have bolt on caps for the u-joints. The small block Corvettes had straps that went on top of the u-joint cap and were held with two nuts at the back of the yoke.

[Keith T.]

Re: 1968 Differtial code

Thanks that makes the car complete.

[Keith T.]

Re: 1968 Differtial code

Thanks for the info Jim.

[Anthony S.]

Re: 1968 Differtial code

Keith,

I checked the Pocket Specs Guide & '68-'69 JG & they say that the "AV" code is for a 3.08 Posi for a 427 engine.

The correct code for a small block with the 3.08 posi is "AL."

Also, I cannot find a plant code for the "S." The axle plant codes for '68 were W, G, B, & K. I believe that the Warren, MI "W" plant was the main source for the axle units.

Anthony

[Terry M.]

Re: 1968 Differtial code

Keith,

I checked the Pocket Specs Guide & '68-'69 JG & they say that the "AV" code is for a 3.08 Posi for a 427 engine.

The correct code for a small block with the 3.08 posi is "AL."

Anthony

Unfortunately Anthony, you have an older version of the pocket Spec Guide. The most recent version more correctly makes no reference to 427 (or in other cases 454) for certain axle codes.

The explanation is too confusing, but that style of rear axle was installed on far more Corvettes than those equipped with the Mark IV motor -- for example it was installed in ALL M40 applications. Check the production numbers and you will find more M40s than Mark IVs in every year. It would be more appropriate to describe that rear axle as "with auto," but that has no macho ring to it and is just as inaccurate. Unfortunately the way Chevrolet described this application has lead to a lot of confusion, some of it even by authors of the NCRS Pocket Spec Guide.

[Anthony S.]

Re: 1968 Differtial code

Terry,

I'm glad to hear that, I felt like I ruined Keith's day.

I guess this would be another update for the 4th edition of the 68-69 JG.

Thanks,

Anthony

[Keith T.]

Re: 1968 Differtial code

Thanks to all for the information.

No day ruined here, this is fun unraveling the car's identity. It was easier to check the engine and transmission as they have the VIN number on it.

Glad to know the last piece of the puzzle fits.

[Jim T.]

Re: 1968 Differtial code

Kieth my NCRS Spec Guide is the first edition, sent to me by the NCRS when they first became available. I did not include the (427) because from the same publication it is shown for my 1970 that the rear end ratio for my car's CAV stamping is a 3:08 Standard (454). From a GM parts book page it is identified as a heavy duty rear end. I do have the caps retaining the u-joints to the differentail yokes.
I did not include the (427) because I knew it was not correct.
Another posting mentioned that SB used straps. My original owner 70 is a SB and has caps. Your automatic (turbo 400) could have caps as well. I do not know if this started in 68 or later.
Terry M. can confirm this, LT-1's had caps, not straps.

[Keith T.]

Re: 1968 Differtial code

Thanks Jim,

I am going to drop the gas tank and see if the build sheet is still there.....this should clear up the confusion.