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------------