Thread: saginaw to m20???

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right now i have a saginaw 4 speed from and older nova. i have been offered an M20 for $400. now i'm going to get it nonetheless, but i was looking to learn some more information on it. as of right now i'm building a hopefully a 500hp small block 400 (11.75 compression, solid roller, TFS heads, etc.) i would like to know,

What are the Gears Ratios in the M20s?
What kind of weight will i save by going to the aluminum case?
I heard M20s are good for about 450 lbs of constant driving...true?

Also, my friend told me that the aluminum case will twist and break easier than my saginaw, should i be worried with my combination?

It will be going in a 1960 Chevy Truck, so there is NO factory transmission cross member at the tail shaft. Just the Front plate and the bell housing cross member, then it's hanging all the way to the pinion. should i put in a transmission cross member or will i be ok without it??????

i had run the saginaw with only two bolts holding the top ears to the bell housing and nothing broke.....given it's a cast iron case and only 300-350hp........

please any help is much appreciated

Thanks

I have used many M20's & M21's and saginaw 4sp's. The only time I had problem was when I has a 454 450hp in my '67 Camaro/4sp with a V-gate shifter and a 12 bolt posi & slapper bars. I twisted 2 M20's in half thur the the main case, I replaced it with a saginaw with V-Gate shifter and never broke another one.
I did a lot of street racing then.
I know many will say that a saginaw is not strong enough, But I have a saginaw 4sp with another V-Gate shifter for behind my 392 Hemi and 2 spares incase I pop one. If you google saginaw you'll find how to ID the stronger one, they have 1, 2 or 3 grooves around the input shaft. Mine are the stronger ones, which I believe is the 3 groove. All my info is locked in my other computer which won't boot up! , and my tranny's are still buried in my shop from moving. I like both.

Oh, wait, I did break the M20 in my '65 Impala with a stock 396, 4sp, posi. (Heavy car)

With your rear mounts being on you belhousing, it is stronger, and you won't have the chance of breaking your belhousing.

Good luck which ever way you go.

My .02 worth!

Pat

ok thanks....i heard a lot of mixed stories about the saginaws, so i didn't know what to think. but i do want take some weight off my truck and figured an aluminum case would do that.....i just don't want to expect too much from the transmission and have one go south on me. especially one that's worth something you know?

so my bellhousing crossmember should be more than enough? i don't need a crossmember on the tailshaft? would i be pushing the muncie too hard with my combination?

also, where could i get a v gate shifter???? hurst has discontinued theirs, and i can't afford 700 dollars on a Long shifter......

thank you again

With the mounts on the side of the block, and the tranny, the belhousing becomes the weak link (Aluminum belhousings), with the mounts on the front of the block & on the belhousing, it doesn't tend to bow at the belhousing.

Most all racers use that type setup. you can also drop the tranny with only pulling the driveshaft & shifter handle. You can even change the clutch & pressure plate without pulling the belhousing.

I got the V-Gate shifter I have now, new in the box at a swap meet fo $25.00 mine is a Mr Gasket, I believe. It's packed in the shop with everything else.

Pat

you aint gonna want a v-gate for daily driving!

Depends on each person, I drove my Camaro 2yrs everyday with it, and then in my V8 Vega for about 4 yrs everyday, I had no problems with it ever! I liked it so well, I got one for my '27 T Coupe. You only need to pull up with your two fingers when down shifting, put in neutral and push the small knob for reverse. But the inline shifting is much nicer then the H gate pattern, and you'll never hit reverse, and you don't have to think about it going thru the H, if your linkage bushing have wear.

I'll keep mine!

Pat

How the transmission holds up depends on how you drive it.

Saginaw Ratio's

Number of ID Grooves
..............................1st 2nd 3rd 4th
No Grooves...............2.84 2.01 1.35 1.00
1............................2.54 1.80 1.44 1.00
2............................3.11 2.20 1.47 1.00
3............................3.50 2.47 1.65 1.00

Muncie Ratio's

Suffix 1st gear ratio
A 2.52:1 wide range
B 2.20:1 close range
C 2.20:1 Rock Crusher

What's nice about the Saginaw transmission, if you get a 2 or 3 groove (this is grooves on the input shaft) you can run a taller rear end gear.