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

What are the book/order form limits for '65-'69 Passenger, Chevelle, Nova and Camaro L-78 or L-72 cars with an M-20? As far I know it depends on the rear gear ratio, but what are the "rules" and are there documented exceptions? If you ordered a 4-speed in place of the standard HD 3-speed and a highway gear (say 2.73-3.31) then you were given the M-20, but if you ordered a deep gear (say 3.55-4.88) then you were given an M-21. I think the limits I listed are correct for '65-'66 passenger, but for '66 Chevelle the limit is 4.10 with M-20. Why? What are the limits for the other years/cars? One of the main things that made me ask/question this was the post of the first '67 BM Chevelle. The car originally came with an L-78, M-20 and 4.56:1 rear. Did they change the option limits for '67 Chevelles? Is M-20 listed on the original paperwork for the car? As far as I know the P.O.P. does not specify M-20 or M-21.

I'm just trying to figure out why and how things were done/ordered. If you have any info, original documentation with the option details for either car/year or think I'm off on something, please post.

Thanks, Paul

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

I own the 67 BM Chevelle you mentioned. The POP lists the L-78 and the 4.56 gears (later changed by Motion to 4.88's) The original magazine article states it had an M-20 and the original owner confirmed this, however you are correct the POP only indicates a muncie, not which one, and the original trans is no longer with the car.

Another interesting one is the former Capt. Carl '69 Garnet Red COPO Camaro that received an M-20 from the factory and has original paperwork to prove it.

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

I thought you had to specify if you wanted the wide ratio or close ratio(M20 vs M21) when you ordered the car. I know there are quite a few 69 Z28's out there with M20's in them with 3.73 gears like mine. If there is a general rule that GM used to determine when a car got the M20 vs the M21, then I'm not aware of it.

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

On Pontiac GTO's 68-70 you recieved the M-20 with all gear ratios EXCEPT 3.90 and 4.33. With those ratios the higher (numerically) first gear ratio would have made 1st gear virtually unuseable.

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

I don't know of this counts but I know of a 1967 Corvette
L-71 (427/435) with an M-20 with a 3.73 rear? Thought this would pretain to the subject https://www.yenko.net/ubbthreads/imag...lins/dunno.gif

-Dan

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

[ QUOTE ]
I know there are quite a few 69 Z28's out there with M20's in them with 3.73 gears like mine.

[/ QUOTE ]

The 69 RS/SS 350 I did up in the mid 1990's had the original drivetrain front to back and it was an M-20 with 4.10's.

I'm wondering if there were different circumstances between BB and SB https://www.yenko.net/ubbthreads/imag...lins/dunno.gif

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

My 70 nova L78 had a M20 with a 3.55 rear Schonye

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

Most small blocks respond better with a lower first gear. (M20) Especially a Z/28. They have no torque. I have the original M21 in my Z. Fortunally it has 4:10's or it would have a hard time just pulling out. I have a fresh M20 ready for it, just to lazy to change it. BB's have more torque so the M21 is a little better in mid range I believe. I think you could probably get what you wanted back then. https://www.yenko.net/ubbthreads/imag...ins/3gears.gif

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

I remember alot of older magazine articles stating that they got the best 1/4 mile ets by revving to about 4000 and starting in 2nd gear. It would cause the engine to fall from the peak torque range there by allowing the tires to hook up. Then the engine would come in to the fat part of the torque curve with the car already hooked and rolling so you wouldn't have to baby it off the line.

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

tony(mrmotion) how is it checked off on your original canadian doc'd jan 68 L78 M22 4.88 factory, on the dealer order form you got from the original owner professor Mas----. https://www.yenko.net/ubbthreads/imag...ns/naughty.gif

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

I recently sold an unrestored '69 Z28 with original M20 trans and 4.10 rear. It had great pedal response at low speeds unlike any other Z I have owned.
There was also at least one Canadian Copo Camaro built with an M20 trans.
Mark

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

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.

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

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

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

I think the M-20 was the std trans unless you ordered the M-21, at least in the world of Novas. My red 70 is a strpped down car, sold off the lot and has 3.55 w/M-20. The other 2 were ordered cars with more options and both came with 3.55 and M-21. The 68 and 69 cars are both M-20 with 3.55 gears. The M-21 seems to be better suited to gears 3.55 and up in the BB cars. Just my two bucks worth.(inflation)

TW https://www.yenko.net/ubbthreads/imag...ins/3gears.gif

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

I think the M20 is what you got if tou did'nt specify something else. I ordered my 70 with buckets, console, 8 track etc, so It was'nt a striped down model and it came with the M20. I did'nt mind the M20, but the Muncie shifter sucked. Schonye

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

I agree with Wilma there, M20 was standard unless you ordered the M21 or M22 regardless of rear gear.

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

And I agree with Marlin.

The paperwork on my Van Nuys 68 Z28 shows the M21 and 4:10 gear as optional selections. Standard Z28s' usually came with a M20 and 3:73 gear.

On the other hand, I have seen a documented 68 L-78 with a 3:07 non-positraction gear and a M22. Seems that GM cooked up some unusual combinations at the time. Original documentation and/or carefully decoded numbers seperate the originals from the clones.

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

Thanks for the responses. Keep'm coming.

I was looking on CRG's site for info. They don't get very detailed, but they do list what was available in a chart. (I'm not sure how accurate it is, but it's getting a little closer.) I'd like to see some info and details from original documents to back it up and for the other years/cars.

For '67
Z28: M-21
L-78: M-13 (3-speed), M-21

For '68
Z28: M-21, M-22
L-78: M-13, M-21, M-22

For '69
Z28: M-20, M-21, M-22
L-78: MC1, M-20, M-21, M-22
L-72: M-21, M-22

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

I was going to do some digging before I posted, but the above post drew me in. https://www.yenko.net/ubbthreads/imag...mlins/wink.gif

That info is correct for Camaros (except L72 could get M20's, I'll correct that). I'd need to do some digging to find the backing documentation, but the jist of it is the M20 wasn't available in a Z or L78 in 67 or 68. In 69, any Camaro could get an M20. Not sure of the logic behind it and have no idea on other models.

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

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.

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

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

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

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.

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

[ 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.

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

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.

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

Thanks for the detailed info Greg! A topic I only have a glancing knowledge of, happy to have it explained much better than I did.
So, were the Chevrolet Price Schedules an independent document or was it part of the dealer books that show up on ebay or ???

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

Kurt,

I think they are part of the dealer books. But since they were updated so often it is possible that they might be found loose. I have the 1970 Nova version from Ebay. I would like to get a full set of the updated sheets but with the price of dealer books these day, I would need to win the lottery a few times.

Can anyone with a dealer book confirm these are part of it?

Greg Roberts

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

My 68 SSL78 has Canadian GM Documentation that shows the Close ratio M22 and the G80 positraction with 4.88 gears. The Sales Order is exactly the same. Up to 69 it looks like GM allowed an "open order" process. In 69 they seem to have restructured the order process to reflect manufacturing efficiency.

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

I have a VanNuys Built 1969 Camaro L78 which has an M20 with 3.55 posi.

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

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.

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

Another good reference source are the Chevrolet Communication kits.These are the monthly boxed kits filled with Booklets and letters,as well as 35mm color filmstrips/records previewing the cars.
They were sent out to the Dealerships to inform the Salesmen whats what.The information,not to mention the color stills & narration are the closest thing you can get to stepping back in time! https://www.yenko.net/ubbthreads/imag...ns/burnout.gif
I collect all of these,& can dig out a desired model year sometime,to see if there is any mention of the transmission availabilty.

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

Mark,
I agree that that the GM documents are good sources of info. It's the 3rd party documents that may not be as reliable.
Even then, GM documents have errors in them. There's always disconnects between marketing and production. https://www.yenko.net/ubbthreads/imag...lins/smile.gif

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

mssl72;

Thanks, I just do not have enough facts to provide a complete picture. I have an updated version that is not complete.

I have several years Service Bulletins and Chevrolet Service News in the binder too. No Price Schedule. There was a full size Fact Book I think as well. The Dealer Sale Album is the wrong size.

Greg Roberts

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

Greg,
The 1966 Sales Album is 13 3/4" x 11 3/4", pages inside are 11 1/2" square. I didn't mention it's measurements before. The Finger Tip Facts book is a 3 ring binder, has 8 1/2" x 11" pages and was "intended to supplement the 1966 Sales Album, and for convenience in quickly locating needed information". That's how they describe it on the second page. Did they have a Finger Tip Facts for 1968? I also have a 1966 Engineering Features book (8 3/8" x 11") and a 1966 New Product Training Booklet (8 1/2" x 11"). I keep my eyes open for other books when at swap meets or cruising ebay.

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

Back around 1970 Alger Press in Oshawa was printing service manuals for GM. They probably printed other stuff for GM as well.
Our COPO Chevelle came with the M20 and the 4:10 gears. We had an M20 in our L78 4:10 geared Chevelle while freshening up the original M21. I prefer the M20 for street driving. A drag strip comparison might be interesting.

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

To do a Comparison is easy.

With a M20 you launch real good and then fall on your ass when you hit 4th gear.

The RPM drop is aroung 1,000 RPM in each gear till you hit 4th where you drop 1,500 RPM, which will really kill your ET's. The M21 is more even at 1,000 RPM drop in each gear all the way through. less RPM drop the longer your motor is up in the power curve.

Pantera https://www.yenko.net/ubbthreads/imag...iggthumpup.gif

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

There was a test done way back by Royal Pontiac----In this test they used a 3sp manual(similar ratio to M2O) and a M21 close ratio 4sp----the GTO had a 3:90----Larry is right in that it had a kick off the line but did fall below the power band--(now the diference might be a little less with the M2O), --the results were .25sec to.40sec and 1 to 3 mph slower with the three sp. depending how tight you wanted wind the 3sp.------For performance you would normally use a close ratio trans with an axle ratio of 3.90 or above,where the 2.20 low would'nt give enough kick off the line with a 3.55 etc.-----Just some added info------------