It has been mentioned a couple times here (including that prior post be "chevymad");
Unfortunately for this discussion, simply calling a "Muncie", doesn't benefit the matter;
Granted when people say "Muncie" 99.8% of the time the 1963-1974 Muncie four speed is being implied. What seems to often be forgotten these days is that the "Muncie" name is an implication of the manufacturing facility, moreover the city that they were manufactured in.
The Muncie plant made many transmissions, and the M-20/M21/M-22 are what most people think of these days.
There were at least two in-house GM three speeds manufactured at the Muncie plant.
The first in house Muncie three speed was manufactured from 1955 through 1965 - I understand these were the base "M12" RPO transmission in 1964, and replaced with the Dearborne unit in 1965. I do not know much about these three speeds.
The second was a Muncie three speed manufactured for 1969 through to either 1975 or 1976 - the last year or two it was exclusive to trucks.
This transmission came in two gear sets:
A = 3.03 / 1.75 / 1.00 / 3.02R
B = 2.42 / 1.58 / 1.00 / 2.41R
I found the GM name for the Muncie three speed was SM-330, for reasons of clarity, I will use SM330 from this point forward.
The SM330 was used mostly under RPO's MC1 & M13 - but the RPO doesn't mean it will be a Muncie three speed.
The SM330 was intended as an in house replacement for having to source the Dearborne three speed, and by all accounts it is indestructible.
I have never come across any first hand accounts of people having any issues with the SM330, it seems most were simply swapped for a four speed - not because anything was wrong with it, but a four speed had cool factor in spades over
any three speed.
As far as I'm aware, the SM330 had Chevrolet division exclusivity for the 1969 model year, and was used as the base transmission in all 1969 Chevrolet SS396 vehicles.
For 1970, Chevrolet appears to have required a four speed for any Super Sport, but for 1970 & 1971 non-SS Chevelles with big blocks did received them as base equipment.
It is my understanding that Buick and Pontiac used the SM330 first in 1970, I am pretty sure I know what years Pontiac used it, but I do not know what other years Buick used it.
I am unaware of Oldsmobile ever using it.
For Pontiac, starting in 1970, the SM330 was either the base, or base-required option for anything more than a 350-2bbl depending on the model in question.
It was the base transmission for 1970 through 1973 GTO's.
For the Lemans line, the SM330 continued to be available through to 1974.
It was the base transmission for 1970 Formula 400's, and 1971 Firebird Formulas with either the 400 or 455HO engine.
It was optional on 1970 & 1971 Firebirds as the "heavy duty 3 speed" option for 350-2bbl cars.
After 1971, the SM 330 was no longer offered on Firebirds, and while the 350-2bbl cars still had a Saginaw three speed as base equipment, anything with a 400 or bigger, required a four speed or TH400.
The real trouble with SM330 is that they are nearly identical to the Saginaw three speeds, the quickest, and most sure way to identify a Saginaw from a Muncie is the side cover;
The Saginaw three speed has a single centred "ear" bolt boss:
The Muncie three speed has two "ears" on either side of the top of the cover:
In nearly every other way, the Muncie three speed looks like a Saginaw - except the castings are all unique, and other than maybe the output seal, nothing can be interchanged.
To answer the original question (title):
It depends on which three speed you're speaking about;- As far as I am aware the Saginaw three speed has a torque rating somewhere around 300ft-lbs, which was why it was never behind anything high powered, or with high torque ratings.
- As far as I am aware, the Dearborne three speed is stronger than the Muncie four speed.
- As far as I am aware the Muncie "330" three speed was stronger than the Muncie four speed.