Rear Code Question

[Erv M.]

My 1969 SB was equipped from the factory with a 3.08.1 ratio positraction RPO# G81 on the invoice a code of 2G81EA. The code stamped is 1AV01169W which in the TIMJG states it is for a P 427 application. It utilizes U-shaped clamps on the axle universal joints.

The date works fine as the car was built February 15, 1969. I am the third owner of the car and can not be sure it came that way. I have spoken to the second owner and he states it had never been taken out, who knows.

Is it possible this is the correct rearend?

[Wayne M.]

Re: Rear Code Question

My 1969 SB was equipped from the factory with a 3.08.1 ratio positraction RPO# G81 on the invoice a code of 2G81EA. The code stamped is 1AV01169W which in the TIMJG states it is for a P 427 application. It utilizes U-shaped clamps on the axle universal joints.

The date works fine as the car was built February 15, 1969. I am the third owner of the car and can not be sure it came that way. I have spoken to the second owner and he states it had never been taken out, who knows.

Is it possible this is the correct rearend?

Yes, quite possible, but I can only show an example using C2 cars. I think you're mixing the ECL code (exclusion code letter ?) which is the suffix on the tank sticker, with the stamped code on the bottom of the differential carrier. The two probably never matched; don't know why .

This example is from 1967: The ECL of EA is for a 327 with 3.55 posi ratio, whereas the stamped assembly code is AN. Want something really confusing ? The 3.70 ratio is stamped FA for 427's, but the FA code on the build sheet (2G81FA) is for a 3.70 on a 327 !! And so on ...

Maybe someone with C3 data can post confirmatory info, but I kinda doubt that the ECL's are available for post-C2's. Someone will surely chime in.

[Erv M.]

Re: Rear Code Question

According to the Stingray Guidebook by Rick Bizzoco the AV code was for a 3.08.1 ratio and all 427's were equipped with HD rear axles which helps me. The Judging Manual states the AV was for 427's without HD which is a direct conflict. However the Judging Manual states that the code can not be seen during field judging so I wonder if they spent a great deal of time on the codes and application within the Judging Manual.

Probably most of the gurus are at the convention so I will wait to hear some feedback.

[Joseph H.]

Re: Rear Code Question

Erv,
Did you ever get an answer to this question. I have a 69' conv 350/350
with a rear end coded OAW 198 E 3, which according to the TIM/JG is for
a 427, HD posi. I have no owner history for my car, but I am wondering
if my read end is what the car came with also.

Regards,
Joe

[Erv M.]

Re: Rear Code Question

I have not had many responses but the lucky and knowledgeable ones are attending the convention. I hope that I will receive some feedback after the convention.

[Erv M.]

Re: Rear Code Question

Calling those in the know concerning C3's.

Can someone shed some light on this issue?

[Terry M.]

[Joseph H.]

Re: Rear Code Question

Terry,
I do not know, as I have no docs with my 350/350 conv. My rear end is stamped OAW 198 E 3 or 0AW 198 E 3. I have U-shaped bolts and the rear end is 3.08 gears POSI.
I am trying to find out if this was the rear end the car came with. It sounds like from this post that it could be the factory original.
What do you think?

Joe

[Terry M.]

Re: Rear Code Question

Well, Joe, there are other ways to tell if the M40 is original, or if a manual trans has been switched in.

Does the frame have a bracket for the clutch cross shaft? Of course if the frame has been changed, all bets are off.

How about the wiring for the kick-down switch above the gas pedal? It might be hard to fab in some original looking wire for that switch, or the wire and connector to the transmission.

Original M40 Corvettes had a bulge on the passenger side floor to accommodate the wider automatic transmission. See the M40 pages of the AIM. It would take a lot of care to add that like the factory did -- not that it couldn't be done, just that most folks wouldn't take that kind of care.

These are just what comes to mind. I think the speedometer cable is different, and there are differences for the gearshift, and the brake pedal as well. Lots of clues there.

[Joseph H.]

Re: Rear Code Question

Terry,
Sorry, I missed the connection with M40(auto trans). My car has the original engine and M20 wide ratio 4 speed, so no automatic.
How does this info factor in here?

Joe

[Erv M.]

Re: Rear Code Question

Terry,

I had to wait to get my car back from the shop to check out the differential. Took it to a NCRS recommended shop so it took a month but very satidified with their work. Got it back to day and my Ujoints are the U shaped clamps!

According to Stingray Guidebook by Rick Bizzoco the 350 axle was lighter duty than the 427 axle and had smaller universal joints and axles. He states that two different rear axles are used in Corvettes, one for the base Corvette 350 cu in and one for heavy duty use(this is my car). All 427 equipped cars used DH rear axles. His book does indicates the AV code is not a HD application.

What reference are you stating the GM classifies the AV code as HD?

[Terry M.]

Re: Rear Code Question

Terry,

I had to wait to get my car back from the shop to check out the differential. Took it to a NCRS recommended shop so it took a month but very satidified with their work. Got it back to day and my Ujoints are the U shaped clamps!

According to Stingray Guidebook by Rick Bizzoco the 350 axle was lighter duty than the 427 axle and had smaller universal joints and axles. He states that two different rear axles are used in Corvettes, one for the base Corvette 350 cu in and one for heavy duty use(this is my car). All 427 equipped cars used DH rear axles. His book does indicates the AV code is not a HD application.

What reference are you stating the GM classifies the AV code as HD?

I don't see where I said AV was HD. What I said was that all Mark IV AND ALL M40 AND LT1 got the differentials with the bolt-on caps. The source of that information is, as I recall, the AMA (Automobile Manufacturers Association) specifications.

Chevrolet called those differentials with bolt-on caps HD in the bulletins they sent to the dealers at the beginning of the model year. I will have to look at those bulletins to see what they call the AV code. I'll let you know, but if the NCRS Spec Guide (the older editions) or the TIM&JG call out the AV code for 427 that tells me Chevrolet listed it as HD.

Just as an aside -- NCRS does not recommend any shop. Maybe some members did that, but the organization takes no position on shops, parts, or vendors.

[Jim T.]

Re: Rear Code Question

My original owner 70 came from the factory, base engine with turbo 400. The standard rear end ratio for the this 350/300 with factory air and automatic was 3:08. All 70 and later C3 Corvettes came with posi-traction.
My rear end stamping as well as what is imprinted on my POP is CAV0702 W.

Like Terry has mentioned, my turbo 400 transmission equipped Corvette has caps, not U-bolts on the differential yokes.

Do not know later C3's, but the 68-72 models with turbo 400 automatics have removable transmission crossmembers. The manual transmission early C3's had welded crossmembers. So there are automatic frames and standard frames.

[Terry M.]

Re: Rear Code Question

My 1969 SB was equipped from the factory with a 3.08.1 ratio positraction RPO# G81 on the invoice a code of 2G81EA. The code stamped is 1AV01169W which in the TIMJG states it is for a P 427 application. It utilizes U-shaped clamps on the axle universal joints.

The date works fine as the car was built February 15, 1969. I am the third owner of the car and can not be sure it came that way. I have spoken to the second owner and he states it had never been taken out, who knows.

Is it possible this is the correct rearend?

Well Erv, I did the research for you.
The 1968-69 TIM&JG (Third Edition) states AV and CAV code is "P 427." It does NOT state HD. Above the chart is paragraph explaining the term HD relates to the use of the block-clamps.

The 1969 Chevrolet Information Bulletins (there are two. One dated Sept 19, 1968, and the other dated April 14, 1969) both list AV as 3.08.1 Positraction, with no HD notation.

From these I would conclude your differential was built with U-clamps for the universal joint attachment to the stub axles.

[Terry M.]

Re: Rear Code Question

Erv,
Did you ever get an answer to this question. I have a 69' conv 350/350
with a rear end coded OAW 198 E 3, which according to the TIM/JG is for
a 427, HD posi. I have no owner history for my car, but I am wondering
if my read end is what the car came with also.

Regards,
Joe