The transmission is in good shape and shifted real smooth. The two reasons I swapped it were to get the overdrive for highway use since I have the 4.56 gears and it was easy to get out while I was swapping the engine. The clutch was a little heavy for my taste and I figured I'd get a new one to go with the new aluminum externally balanced flywheel on the ZZ383.

I sent you a pm with more details.

 

Replied.

 

You can go with either ratio box with that deep FDR, as the rule of thumb many subscribe to is not to go close with less than 3.70. Have you plotted out the shift points of the two??

Just as a reference, I'm planning on putting the Italian M22 wide ratio gearset in between my 496 BB and 3.55:1 rear. Tried the 4.11 at one time, but found it to be impractical for my needs.

 

The Super T10 of that era with the 2.43 first gear were the strongest trans put in a C3 except the Muncie M-22. The T-10's with the wider ratios were not as strong. That would be a great option and would use a Turbo 400 yoke. Had one of these in my 63 when I got it and beat the snot out of it and never hurt it. I used to tear out muncie's on a regular basis in my old Camero. The Super T-10's are a lot cheaper and easier to find than the Rockcrushers.

 

Justin wide trans ratios are good when your faced with something
like your original 3.08 rear ratio, the bigger engine you
have the easier it is to pick up the wider gear spread .The close
ratio with 2.43 X 4.10 gives you a really nice 9.96 low gear
has nice close gear spreads for your smaller 350 to work with.

My first post was a loaded question far as I know the later
70s super T-10s were stronger then the M/20, M/21 there
were a lot of them put in things like 79 Z/28 camaro and the vettes.
Just guessing but I would think the later 70s
firebird trans ams/formula firebirds would have Super T-10s.

Borg Warner did make an over the counter super T-10 with
a steel case. probably would be hard to find one.

 

I'm looking for value and strength I don't want to tear it up when I am romping on it. I guess either a super T-10 or a m21 is what I should go with. Since the m-20 is a wide ratio, right?

 

While I certainly dont want to try to talk you out of the 4 speed,
I hope you dont think that it will take more abuse than a TH350 will.
The TH350 is probably more durable than the 4 speed.
That being said, I'm running a Super T10 in mine.

 

Here are your mph at redline for an M20 (wide ratio) vs M21 (close ratio) assuming a redline of 6k rpm with 27 inch tires and 4.10 rear gears.

M20 M21
1: 52 60
2: 70 80
3: 90 103
4: 131 131

You'll get slower off the line acceleration and it will feel a little more sluggish in 1st through 3rd with the close ratio transmission. You still have a 20 mph difference between each gear except for the 3-4 transition. The close ratio just means the jump from 3-4 is smaller than in the wide ratio.

Either way you will still be turning 3200 rpm at 70 on the highway.

Check out http://www.5speeds.com/muncie2.htm for more info.

 

So guess a wide ratio would be fine since I want the most off the line I can get. As for the th350 being stronger than a 4 speed what are other peoples take on that?

 

Just skip the M-20 find the later super T-10 in either a close or
wide ratio, I think the later wide ratio had even more of a wide
spread between low and 1.1 high gear. probably more like 2.88
low gear.

Most of the cars that came off the showroom floor not 100 percent
but most were geared like this

3.O8 was combined with M/20 wide ratio 2.54 low gear

Alomost all the C2 small block high horsepower cars came
with 3.55 with M/21 close ratio 2.20 low gear.

The later C3s with the higher horsepower small blocks showed up with
3.70 with M/21 close ratio 2.20 low or the 2.43 low gear close ratio/

Now lets go back to 3.08s wide ratio 2.54= a 7.82 overall low gear
you had a C2 vette 3.55 close ratio with 2.20 = 7.81 overall low.
as you can see the low gear was virtually identical, the reason
the wide ratio with the first three gears lowered was to make up
for the slugish 3.08 rear end then there was a big drop between
3rd to fourth gear.

If you had a later C-3 with 3.70 gearing they showed up with
3.70 X 2.20 close ratio= 8.14 or a 3.70 X 2.43 close ratio= 8.99.

I have had both M/20 and M/21 with 3.70,3.73, 4.11 with 3.02,327
350, 396, 454 engines.

I have had the 2.43 X 3.70 in my 78 L-82 vette
and a 2.64 X 3.73 in a 79 Z/28 camaro.

You don't have the slugish 3.08s to put up with, I like the close ratio boxes with 3.70/4.11 gearing. But just find the later super T-10
trans. yrs ago when people built street strip cars they used a
4.56 X 2.20 close ratio= 10.03.

If you use the 2.43 close ratio with your 4.10 you will end up with
a 9.96 can't beat it with a stick. if you find one of the later wide
ratio trans that were ment to be in front of a 2.73 rear gearing
I think there low gear was around 2.88. you will end up at
4.10 X 2.88= 11.80. low gear

If you use this kind of gearing with your making power to 6000 rpm
hydraulic cam, your first gear will be virtually worthless, may as well
take off in second everwhere you go, also 2nd and 3 rd gear with
the even lower ratios of the later trans combined with 4.10s they will
be very short shifted gears with your 6000/6300 power band.

Let me give you a comparison on the 11.80 low gear to the past.
if you took a car and decided to drive it on the street with
the 2.20 close ratio M/22 lets say you ran it around with
5.13 rear gears 5.13 X 2.20= 11.28 now 11.28 is not as low as
11.80, I have ran around on the street a little bit with 4.56, 4.88, 513s
and 2.20 low gear and trust me there were no cams in the cars that fell
on its face at 6000 rpm, without any slicks on the car (5.13s)with even
the no torque at low rpms cam, first gear was totally worthless for anything at all it would just wipe out the tires with ease even with the big cam. This was just a cammed up 331 size engine.

My point is you can go from one extreme of a 7.82 low gear or another extreme
of a 11.0 or higher low gear.

I tore a damn worthless M/20 trans out in my 66 vette with 4.11s
331 small block, I think the rear tires were around a 9.75 X15s radial tires.
I personally would not give a dime for a M/20 wide ratio trans. If you buy
one don't be power shifting it drive it around like an old woman.

 

well, I want to be able to beat the living crap out of it and have a good (useful)1st gear. If I was to go with a super t-10 what years would I want to look for?

 

Little Mouse is right on the money!
Everything you need to know to identify Super T10 and ratios.
http://fiedlerh.home.att.net/BW.htm
Looks like corvette applications are 1976 - 1979 L82 with M21 (BW)
Firebird w/ 400 or 455 1973 - 1979
Go with the 2.43 ratio. They are the strong ones and best suited to your rear end ratio. Look for 2 rings on the pinion shaft. If you can find an iron case one they are the very best. They are aftermarket w/ hi nickel gears.