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Old 04-09-2010, 06:05 PM
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m-20, hOW MUCH hp WILL SHE TAKE

Rebuilding my M-20 because she is getting pretty dran noisey.
Converted my 65 to a 4spd from a auto. 454 in her now, but plans
for a mild 496. Have scatter shield. How much will this M-20 take?
I am not going o be trying to get rubber in every gear all the time at all.
BUT..!! will want to loose some on take offs sometimes and maybe bang
2nd once in a while.
I know everything breaks, but want to stick with the 4spd.
Thanks in advance.

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Old 04-10-2010, 11:20 AM
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Not much. Not a 496. Unless you get hard tires and keep lots of air in them. When I was younger and abused everything, I used to have better longevity with Saginaws than Muncies, because of the weak case I was told.
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Old 04-10-2010, 11:43 AM
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The M-20 is a noisy trans anyway, So yours is making more noise then normal i guess? Find a B-W Super T-10 it's a real good trans IMO.


Cole
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Old 04-10-2010, 12:01 PM
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Quote:
Originally Posted by lmsport
Not much. Not a 496. Unless you get hard tires and keep lots of air in them. When I was younger and abused everything, I used to have better longevity with Saginaws than Muncies, because of the weak case I was told.
For some reason I had it the other way around, never broke a muncie but I easily wrecked 2 saginaws!
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Old 04-10-2010, 12:09 PM
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If you decide to loose the rock crusher you have now, and don't go with the B-W Super T-10, Look for a M-21 It's a good trans also.JMO I always had better luck with the B-W or Muncie trans myself. But have seen people run the dogs off with a Saginaw trans. Just never my case. JMO I passed on a M-22 last year wish i went ahead and got it now.


Cole
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Old 04-10-2010, 01:35 PM
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Quote:
Originally Posted by eloc431962
The M-20 is a noisy trans anyway, So yours is making more noise then normal i guess? Find a B-W Super T-10 it's a real good trans IMO.


Cole
I hope mine doesn't turn out too noisy- I know the M-22 has straighter cut gears than the M-20/21's and make more "whine".

I had always thought GM went to the Muncie over the T-10 in HD apps, but I certainly could be mistaken...

I will say this: Neither the Muncie OR T-10 is going to stand up to a high torque BB engine if you get even a semblance of traction. Failures might start w/the u-joints, the driveshaft itself, the axles or diff- but it WILL get to the tranny. One way or the other.
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Old 04-10-2010, 02:55 PM
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Quote:
Originally Posted by cobalt327
I hope mine doesn't turn out too noisy- I know the M-22 has straighter cut gears than the M-20/21's and make more "whine".

I had always thought GM went to the Muncie over the T-10 in HD apps, but I certainly could be mistaken...

I will say this: Neither the Muncie OR T-10 is going to stand up to a high torque BB engine if you get even a semblance of traction. Failures might start w/the u-joints, the driveshaft itself, the axles or diff- but it WILL get to the tranny. One way or the other.
Your right Cobalt the M-22 Is the real noisy rock crusher trans, I got them mixed up sorry bout that. And you are right about them holding up against a built up Big Block if it ever hooks something gonna give


Cole
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Old 04-10-2010, 03:21 PM
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Cole, how many guys do you suppose pulled the cover on a M-22 and said, "****, this isn't a M-22! Those teeth are not straight cut!!" LOL

For those who've not seen the slight difference between the M-20/-21 gears and the "straight cut" M-22's:
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Old 04-12-2010, 11:28 AM
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4spd Behind BBC Strength Thanks 4 Suggestions

Thanks a ton for all the comments. I really want to keep my
65 a 4spd or 5spd. So even the M22 would explode behind a
stout BBC? What about the 70 Chevelle LS6? M22 was in those??
What about the new super case that the Muncie guys are using to
build Muncie's these days? Plus they are using the steel plate between
the front and back sections now. Thoughts??? or suggestions on what will
hold up behind a BBC? The Saginaw is cast iron case and all the Muncie's are
aluminum. Plus I have 3:31's in the rear so I cannot go close ratio like the M21
or M22 unless I go to 3.73's or up.
Thanks
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Old 04-12-2010, 12:39 PM
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For an OEM 4-speed tranny, my first pick is a toploader Ford. Stock it's a tough SOB, and it doesn't need a ton of work to put it as good as it can get.

Then a "Hemi" A-833 MOPAR 4 speed. It was also used in some 440 applications, has the 18 spline input instead of the 'regular' 23 spline. Some guys don't like the shift 'feel', it has to be shifted, not nudged. More to do w/the leverage of the OEM shift levers, than a problem w/the transmission, IMO.

Then a Super T-10. Tex Racing has modified units, as well as others.

Doug Nash makes a tough as nails tranny. And there's always a Lenco, Liberty or Jerico.

If you want an OD, Tremec TKO (450 ft/lb) or TKO II (475 ft/lb) or the TKO 500/600 (~850-900 HP and 500/600 ft/lb). Don't forget your wallet.

Then there are the T-56 and up, but you said 4 or 5 speed, so...
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Old 04-12-2010, 01:09 PM
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Tough 4 or 5spd "cobalt327" Thanks

I saved your responce. I want to find/rebuild/buy or
whatever a 4 or 5 spd that will take the abuse. There is
a 66 Impala out there with a 572 BBC with a 5spd Tremec
I think and I've seen the guy bang through the gears HARD.
Not sure how much they are $$$$ and a Jerico is still aluminum
casing.."how is that stronger"?
Thanks
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Old 04-12-2010, 04:32 PM
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Jerico has absolutely straight cut "spur" gears so there is no thrust load put into the case from the gears meshing. It also has a real beefy aluminum case.

Forget the Nash, it is based of the Muncie and is really no stronger, I have seen the input shaft twisted right clean off of them, my race trans builder told me to forget them.

If you are looking for a stock 4-speed to hold up, as has been said the Ford RUG TopLoader is easily adapted to the Chevy engine, Lakewood even makes a specific Chevy blowproof bellhousing to use this trans
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Old 04-12-2010, 04:39 PM
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Ericnove72, Thanks 4spd Tuffness

there is guy in Portland, OR that has a Jerico behind a BBC 540
stout and apparently it seems to hold up. Finding a clutch type
Jerico 4spd price wise is like buying another used car. Love to have one.
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Old 04-12-2010, 08:28 PM
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Forget the Nash?

Richmond now runs the show. The street version will handle 450 ft/lbs. The race tranny shown has been face plated, otherwise is what you get. Nada wrong w/it, strength-wise!
NASH 4+1 Race

LIBERTY LSC5000

Last edited by cobalt327; 04-12-2010 at 08:36 PM.
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Old 04-12-2010, 10:23 PM
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I should clarify, the old Doug Nash Street 5-speed is not worth a hoot, even the syncro parts interchange with a Muncie. The newer Richmond Race 4+1 version is a stout piece from the looks of it but I have no experience with them.
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