Would a '71 M-20 be an "ok" choice to use for the street/weekend racing? Would this be stronger than a sixties era Borg Warner aluminum cased T-10? What is the advantage of having a close ratio M-21 vs the wide ratio M-20? Other than the ratio differnce between these two four speeds,would durability be equal? If one were to use a M-20,what rear end gear ratio would perform best?
Thanks in advance.


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Larry Santi
72 RS/Z28
76 Malibu Classic

There is no "Set in Stone" standard when selecting a transmission. I recommend most people get a M-20 because of the deeper first gear, you can run a higher rear, and still perform relatively good. If you have a 3.73 or lower rear, go with a M-21, especially with some serious H.P., or step up to a M-22, and get ready to lay down the $$$$.Have M-20's rebuilt :$550 , M-21's rebuilt:$650, and 1 M-22 at this time, rebuilt :$1400.Stick with the later '66 up design, they have a larger countershaftgear pin, and are more durable.In '71 they went to fine spline input/turbo 400 output shafts, but I don't think they are actually any stronger.Actually the M-22 of ' 70 went to this design also, but I don't think you will find one of these laying around.

Muncie & Racing = Broken Wallet & Tranny. Period. Go Ahead and flame me I have A BW Super T10 with a Nodular case. Ask any old timer (shhhhh.)60's drag racer how many Muncies they made junk out of.
Rick p.s. If you must, a 2.20 close ratio was for roadracing and the 2.52 wide ratio was better suited (only because of ratios and in no way because of strength) to the dragstrip.

I beg to differ.
IF BUILT RIGHT,they will stand a tremendous amount of power.
Another point is to make good use of the M23/new order box.
A LOT tougher than the rest of the series Muncies.

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DVC-98.Racing
470 cubes of fogger injected thunder in a 71 z.
racing@mbox303.swipnet.se (http://racing@mbox303.swipnet.se)

Racing> How do you build a Muncie right so that it will quit trying to push the cluster out of the bottom of the aluminum case? Do alot of Bracket or SuperStock drag racers still use Muncie 4 speeds? Rick

Well Rick,i put an HONEST 1000+ through mine.
Trick is to keep the casing from flexing alright.
What we do is that we make or own rear bearing plates out of Swedish SS 2172 steel.
Naturally there´s mor to it than that,but that´s the main improvement.
Yes,we also retemper the gears.
Have to admit tho,that this time out we´re building the "speedchanger" around a Liberty built DNE dragbox.

If you wanna have a look at one of my cars,try; ol´ slo´ (http://home.swipnet.se/mechanixracing)

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DVC-2000.Racing
482 cubes of fogger injected thunder in a 71 z.
racing@mbox303.swipnet.se (http://racing@mbox303.swipnet.se)


[This message has been edited by Racing (edited 01-02-2000).]

btw Rick.
The case in Q IS a 23.
Temper we use is Rockwell C56-58

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DVC-2000.Racing
482 cubes of fogger injected thunder in a 71 z.
racing@mbox303.swipnet.se (http://racing@mbox303.swipnet.se)