Option Codes

[Mike G]

I just dropped the tank on my '71 BB Roadster and was quite pleased to find the tank sticker there and quite readable. I can't seem to find some of the option codes in the NCRS Spec Guide and the wording beside the codes is only partially readable. Can someone tell me what these are:

G81AA (Only can make out the word "Positraction")The guide doesn't list a code for this in '71 only '70. Is it the same? My car was build in late Dec '70 or early Jan '71. Maybe this is why a '70 option code is listed. F62HV (Only can make out the word "Springs") Z49AA (Last word is "Equipment")

Also, the dealer number is either 786 or 796 or 798. The car was supposedly purchased in the northern states near Detroit if the helps narrow it down. Does anyone know what dealership this is or was?

What type of numbers should be in the ID# and Order Number. Are these tied to the VIN?

Finally, the car was equipped with the rear window defroster (option C50). The guide states that only 1598 cars were equipped with this option in '71. Is there any info out there that states how many convertibles had this option vs. coupes? Is there also anything that shows the breakdown of conv vs. coupes that were equipped with an M21?

Thanks.

[Wayne M.]

Re: '71 Option Codes

Mike --- Interesting; Can you read the zone # (to the left of dealer #) ? Z49 option (at least in '72 & "73) refers to Canadian Base Equipment. Detroit is just NORTH across the river from Canada. You're in luck if it's a Canadian delivered car, because you can write GM Canada, and, for a nominal fee, they will check their import records and send you an official copy of the dealer and options.

As to the F62 spec, my original '72 (Canadian base engine 4-sp conv.) had code F62HS5. I see LS5's on the '72 list with spring codes F62HV5. Unfortunately, I don't have any '71 lists.

[Chuck S.]

Re: '71 Option Codes

Wayne,

I think you are right about the F62HV being a spring code: the front spring broadcast codes for '70-'72 were HS, HT, HU, and HV. Note that "HV" is the last two characters in the option code. That code was for the highest spring rate, i. e. 454 loaded with AC, etc. Your code F62HS5 has "HS" embedded in the code indicating a small block (which it is), without AC(?).

The G81AA may only indicate positraction (standard equipment) or it may indicate an optional axle ratio. It would be interesting if Mike could read his axle code and find out if he has an optional ratio.

Chuck Sangerhausen

[Roberto L.]

Re: '71 Option Codes

I think that G81AA means a positraction axle (in my 70 sticker reads G81AF positraction axle) as Chuck commented. There is a separate code for rear axle ratio (GV4AB or so). Roberto, NCRS #30019, RMC

[Chuck S.]

Re: '71 Option Codes

Halo Roberto!

In 1970, those tank sticker symbols only bear a vague resemblance to the ratio code suffix stamped on the differential. I am thinking that in '71 and'72 they probably standardized the differential stamps to the tank sticker codes.

On the differential, the ratio in 1970 is indicated by three letters in the format "CXX" such as CAN=3.55:1. In '71 & '72, the ratio suffix stamps are closer to tank sticker symbols being shared here, i. e. AA=3.55:1, AB=3.70:1, etc. If we apply the '71/'72 differential stamp codes to Mike's tank sticker code (G81AA), it may imply he has 3.55:1 ratio positraction. I suspect the tank sticker ratio "suffix" remained the same all three years, but isn't obvious in the '70 differential stamp.

Is anyone still with me? Roberto, intrepretation of your "AF" sticker code isn't clear by this "theory" because there were no "AF" stamp suffixes in '71/'72. Do you know your axle ratio or differential stamp suffix?

Chuck Sangerhausen

[Terry M.]

Re: Option Codes *TL*

Mike,

G81AA is indeed the listing for Positraction. One of the greater mysteries of the 1970-1972 Corvette is why the positraction code appears on the build information when it is "standard equipment" beginning in 1970.

Others have given you goos info about the F62HV spring and Z49AA Canadian equipment.

BTW: all of those codes and more are in the appendix of the NCRS Technical Information manual and Judging Guide (TIM&JG).

You need the Zone number and the dealer number to tell where the car was intended to be delivered (as opposed to the actual selling dealer). Dealer trades throw this off. NCRS has some zone/dealer codes, but very few relative to the total number.

The ID# and Order Number have no relationship (that we know of) to the VIM. Later 1971 Corvettes had the VIN on the tank sticker. Near the bottom of the sheet in carbon and backwards as if typed from the rear. Key codes are in the same area.

There is no breakdown of Coupe and Convertible options given by Chevrolet except for the 1972 model. All those numbers are in the NCRS Specifications guide - available from the merchandise page of this site, the same as the TIM&JG.

Terry

[Dino L.]

Re: '71 Opt Codes - GM canada address - Wayne

Dear Wayne,

Do you have the address for GM of Canada and what the nominal fee is, how far back (what year corvette) do they have the import records for? Thanks Dino

[Mark]

Re: '71 Opt Codes - GM canada address - Wayne

GM Canada Vintage: 888-467-6853 Cost is $40-$45 CDN and records go back at least until early 60's. Mark

[Wayne M.]

Re: '71 Opt Codes - GM canada address - Wayne

Dino --- Mark is correct; copy/paste this URL to read what they offer.

http://www.gmcanada.com/english/maintenance/parts/maint_vint.html

[Roberto L.]

Re: '71 Option Codes

Hello Chuck, interesting your comments. My base engine 4sp 70 coupe has standard gear (3:36). Code is CAM, I positively verified it in the car sometime ago.

Tank sticker mentions it (03GV4AB Rear Axle 3:36 ratio), positraction is in different item (03G81AF Positraction Axle). You are right, at least in 70 there is no match between sticker code and trans code.

Roberto, NCRS #30019, RMC

[Chuck S.]

Re: '71 Option Codes

Roberto,

Thanks for sharing your axle ratio.

What that means (no correlation between 03G81AF and 03GV4AB codes) to me is no general conclusions can be drawn about the "AA" in Mike's tank sticker code G81AA; if the tank sticker code for positraction didn't indicate the axle ratio in '70, it very likely didn't in '71 either. As Terry said, it simply means positraction rear axle, period.

If a tank sticker indicated only G81AA in '71, you would have the standard axle ratio (3.08(M40,LS5+M20), 3.36(L48+M20, LS5+M21,LS6+M21), 3.55(LT1+M20), 3.70(LT1+M21). Only if you had an additional tank sticker code for optional axle ratio (like yours) would you have anything other than the standard axle ratio.

OK, I'm slow, but I get there. I need to get the new manual as Terry recommended and save myself a lot of thinking.

Thanks for your help Roberto.

Chuck Sangerhausen

[Mike G]

Re: '71 Option Codes

The code off the differential is AXW363E2. I think this is a 3:08. The Dobbins Fact Book lists this as an optional ratio (the standard for an LS5 without air and an 2:20 M21 is listed as a 3:36). The NCRS books don't list the 3:08 as an option (only 3:70, 4:11 and 4:56). Am I reading this wrong?

[Mike G]

Re: '71 Option Codes

The only thing I can make out is a "0". I think that its supposed to have two numbers so I don't think this will help much.

I phoned GM of Canada a month ago and they ran the VIN with no match. The Canadian emissions label is still on the car, this is why I tried.

The previous owner assumed that because they didn't find a match when he tried 14 years ago, that it came in from the States early in its life. Based on the info from the tank sticker, I'm convinced now that it's is a Canadian car.

Consequently, we (my friend and I) spoke to GM again today and he said he would try again. He said that sometimes the microfiche is a little blurry and he may have missed the match. We'll see if he comes up with something. I've got my fingers crossed.

Thanks.

[Chuck S.]

Re: '71 Option Codes

Mike,

For '71, the first two letters of the differential stamp is the ratio code, in your case "AX"=3.36:1. The next letter is the plant where produced; "W"= Warren Motive. The next three numbers is a julian date (day of the year) produced, where 001=January 1, 032=February 1, etc. Yours is "363"=December 29, 1970, a Tuesday (Happy Holidays). The next letter is the source of the positraction unit, "E"=Eaton. The final number is the shift produced, in your case "2"=second shift.

If you have a M21, close-ratio transmission,with your LS5, then you have the standard axle ratio. Check your tank sticker; I'll bet it shows you have the M21 transmission. If you had the M20, wide-ratio transmission, the standard axle ratio would be 3.08:1.

What gave you the idea you had a 3.08? You could have a 3.08, but it would have been a change from the original production ratio.

Fun, huh? Get yourself a '70-'72 Judging Guide and continue the search!

Chuck Sangerhausen

[Chuck S.]

Axle Ratio Follow-up

Mike,

I just realized you asked another question on your original post regarding NCRS references on optional axle ratios.

The old Second Edition '70-'72 judging guide I have lists all the available axle ratios for '71, but it does not attempt to specify which is standard or which is optional for any given powertrain. The new Third Edition may make that specification, but I have not seen the new manual. Terry McManmon may be able to add some detail on this.

You are using exactly the same reference I am in determining the standard axle ratio, i.e. Dobbins Fact Book of 1968-1972 Stingray. The way I read Dobbins chart, I believe Dobbins is saying that there are only TWO optional axle ratios RECOMMENDED for any given powertrain. In your case, where the standard axle ratio is 3.36:1, you would also be able to order an "economy" axle ratio (3.08:1) and a "performance" axle ratio (3.55:1). There is also a footnote for the LS5 with M21 that says "special 3.70 also available". For your car (assuming you do have the M21), I would think those four axle ratios would be the only ones that were available. Terry, or more experienced judges may be able to confirm that for you.

Chuck Sangerhausen