M-20 with L-78 or L-72 & deep gear -How?

[Pantera]

My '69 L-78 7,400 mi survivor Nova has the build sheet showing a M-20 but the tranny does not have a ring around it?

It also has a 3:36 rear.

Could it have been replaced with new gears under warranty?

Trans Case has all the correct numbers on it.

[JRSully]

My original 69 L78 Nova has an M20 on the build sheet, and was ordered and still has the original 4:56 rear in it (gear change was necessary to say the least) SULLY

[mssl72]

This topic is something I have been dealing with recently. A lot of questions have come up, some got answered, others created.

The 1966 Finger Tip Facts book and 1966 Motor Vehicle Price Schedules book both have a page with all the "Power Teams" listed. It shows the engine, transmission and rear axle ratio combinations that could be ordered. I'll list a few examples of what it shows. For Full Size Chevrolet and L72, 427/425hp you could order a 4-speed close ratio (M21/22) with 6 different gear ratios ranging from 3.31-4.88's. If you wanted a wide ratio (M20) 4-speed or a Special 3-speed (M13) it lists only 3.31's, nothing else. The 3.31 ratio was considered standard equipment. In 1966 for a Chevelle ordered with an L78, 396/375hp you could order a 4-speed close ratio with 7 different gear ratios ranging from 3.07-4.88's. If you wanted a 4-speed wide ratio or Special 3-speed you had 5 different ratios ranging from 3.07-4.10's. In Chevelles 3.73 was standard equipment. Corvette with L72 shows only close ratio being available with 4 gear ratios ranging from 3.36-4.11's, 3.55's being standard.
So, for example, why could you get a wide ratio 4-speed (M20) and 4.10 posi in a Chevelle and not in Full Size Chevrolet? Why only close ratio in a Corvette? How did Chevrolet decide things like this? I didn't think that the gears you wanted would effect the transmission you could get. I also found that POP's could tell you Muncie, but not which one. You would need a build sheet or window sticker. I don't have anything on the 1967-1969 model years, but I would love to see what was going on in the same books for those years.

[NCGuy68]

Don't know of any accurate "fact books" that address what gear/tranny/engine combo was available to the public in any given year.

As I've mentioned, original documentation and careful decoding are the acid test.

Correct me if I'am wrong please

[mssl72]

Well, both the books I mentioned and used for the facts I stated are 1966 GM, Chevrolet books. Not something some car guy threw together and stuck a bowtie on it. Both are used by the dealer/salesman with the buyer to order a vehicle and were supplied to the dealer by GM. The books are what they are. I can post pictures of them.

That is the problem, accuracy. Some people go crazy to try to have their car restored accurate and factory correct. If there isn't a build sheet or window sticker to accurately restore a car, then what should be used for reference? No build sheet? No window sticker? It would then make sense to use dealer books, handouts and other GM/Chevrolet documentation. There are other books published out there that are a huge help and when used in conjunction with GM reference materials, help confirm things. If you can get them to all agree with what your trying to find, then that's great. But it doesn't work all the time. Unfortunately even protect-o-plates and build sheets aren't always 100% accurate. For example, I recently saw a build sheet for a '66 L72 Chevy that was delivered the first week of May, 1966. The broadcast code for the carb on the build sheet was EF. EF is for a 1965 L78 carb. Why would that be when approximately 1,000 L72's built before it probably had the correct code EE? "E" and "F" are close on a keyboard/alphabet and can easily be confused at a glance. A type-o?? This car was built at a Doraville which was a BOP plant. Not all plants referenced everything the same. Was there actually a left over Holley 3130 from 1965 that was sitting on a shelf that somebody said "Oh, what's this doing sitting around? Throw this on a car.". If it did in fact come with a 3130 instead of a 3246 there is no way to prove it. I have a good friend that is restoring a 1968 L72 Biscayne. It still has the protect-o-plate. The POP shows the "ID" suffix for the engine code which is for L72. But at position D for the carburetor source code it has an "R". That "R" is for Rochester. Did L72's come with Rochester carb's? They didn't according to all the resources I've seen. Has anybody out there ever seen a Rochester carb on a GM factory Rochester aluminum intake on a L72 427? I don't think so. Here's another example of a conflict as posted by another member of this site.

https://www.yenko.net/ubbthreads/show...o=&fpart=1

What is the end-all reference? Is there one? Not that I know of. If somebody has a build sheet, window sticker and POP, and they all agree, and it all agrees with ordering information, then there wouldn't be a question. If you see an official GM reference that says a certain combination is not available, it brings up a conflict. I think that's why this thread started.

[Kurt S]

[ QUOTE ]
Well, both the books I mentioned and used for the facts I stated are 1966 GM, Chevrolet books......Both are used by the dealer/salesman with the buyer to order a vehicle and were supplied to the dealer by GM.

[/ QUOTE ]

Actually, good chance that GM didn't printed those. Dealers ordered these dealer guides (containing RPO, model, and pricing info) from outside contractors. These businesses consolidated the data that GM provided and sent regular updates to the dealers. These have good info in them and were very useful to the dealer, but weren't directly from the General.

[Nova Research Project]

Here is what I found when doing similar research. There are four types of price and option availability sources.

1. The Chevrolet Price and Fact Book (pocket size)
2. The third party Salesman Pocket Price Guides (pocket size)
3. The Chevrolet Passenger Car Specifications and Manufactures Suggested Retail Prices
4. The Chevrolet Price Schedule 8.5” and 11”

1 and 2 are both compiled from 4. They both are condensed to fit the pocket size and have disclaimers to see 4 for the complete list of options and model availability of the engine/transmission combinations. 3 is even more condensed and targeted for the customer.

Each of these documents was updated at least every quarter. That means that what you could order in September might not be available in January or visa versa.

The salesman validating the option combinations being ordered by the customer used the current Chevrolet Price Schedule and the current New Car Order form. This information might include restrictions between Engines, Transmissions, and Axle ratios. An example is that a Powerglide was not allowed on a 396. It by no means replaced the logic built into the computer design that built the cars. There might have been engineering reasons to add a heavy duty M21 or M22 to an order. Since each of the 4 speed transmissions could be ordered as an extra cost option and the standard transmission was a M20, why give away an upgrade for free.

So we are left with original documentation that was shipped with the car as the only real proof of what was done.

I hope this helps,
Greg Roberts

BTW I am looking for copies of the Chevrolet Price Schedule for the 1968 Chevy II and 1969 to 1972 Nova. I want create a chart of the transmission options. I have started the following Chevy II and Nova Transmission availability. This was created from the pocket price books and does not even come close to what was really available.

[mssl72]

Kurt S. - I'm sorry if I implied that GM printed them. Helm Inc. does a lot of GMs printing and is one of probably a number of companies that does the printing for GM. You're right about some outside companies putting manuals/books together. But wouldn't you agree that the data that is supplied comes from the General?

Greg R.- Nice work on that chart and page! Great info! The Price Schedule that I have came with an almost complete set of Technical Service Bulletins, Chevrolet Service News and other stuff. I found it a few years ago. The Service Department binder that everything came in does have titled dividers for the Price Schedule.

One of the source books I was using is (as Greg R. described it in his response, a #4) a Chevrolet Price Schedule (8 1/2" x 11"). The cover page is dated November 1, 1965, 1st mailing. Most of the pages inside are Dated February 1, 1966 that reflects an updated mailing was put in at some point. The other source book is called Chevrolet Finger-Tip Facts. It is also an 8 1/2" x 11" book and comes in a 3 ring binder. It's like a cross between the Price Schedule book and the Dealer showroom book (Sales Album). It doesn't have fabric samples and is more technical. It was used as a supplement to the "Sales Album". I figured that not everybody has seen some of these books before so, I've put some links here to pictures of the manuals.

The first 2 links are from the 1966 Finger-Tip facts. The first one is the cover page and the second one is the Chevrolet Power Teams page. On the Power Teams page you can see the engine/transmission/axle combinations that were available. This Power Teams page is only for Chevrolet full size passenger cars.

cover page
Power Teams Page

The next 3 links are for the 1966 Pricing Schedule that also reflects this information. I included the Chevelle Power Teams page as well.

title page
Chevrolet Power Teams
Chevelle Power Teams

I did have a conversation with a great friend of mine who has worked for GM for quite a while and he started to tell me how GM came up with these combinations. I don't have it all sorted out on my end, but he is being kind enough to send me some engineering data on how they did this. I can tell you that it involved some obvious things like vehicle weight, engine torque and something I never figured like how many engine revolutions per mile. I'll see what info is in there when it shows up.