The Stovebolt Site Forums The Shop Area Engine Shop Questions... Muncie M21/22 Behind a 235

Hey All,
Anyone here running a Muncie 4 speed box (M21 or 22) or Borg-Warner T10 behind a 235. I'm going to pull the SM420, torque tube / diff. and want to run one of these boxes. (Posted over at ChevyTalk also.)
Project vehicle is a '50 Chevy 1/2T Panel with a 235 motor. Would like to retain the same clutch / bellhousing setup. Would you know what the length of the Muncie tranny input shaft is? (That is: from the end of the shaft back to the face on the tranny where it bolts up to the bellhousing.)
Also what is the shaft diameter at the pilot bearing?

It is late at night now, but I have a Corvette out in the garage with an M21 in it, and the engine out of it still while I rebuild it. I can get that information for you if you can wait 'till morning. I'll be back with answers...

A Muncie will bolt up to a 48 or later truck bell housing,no problem at all,same clutch spline,same pilot bearing .The length is 21 inches from the front face to the tip of the tailhousing.

The input shaft is 6 1/4" from the face of the transmission to the end of the input shaft. The girth of the input shaft, to my best approximation, appears to be about 1 3/16" in diameter. If I had a caliper I could tell exactly.

Thanks Gentlemen, I looked around last night and I think I'll narrow the search down to a Saginaw or a T5. The Muncie boxes seem to be way over priced (IMHO).
web page

I had a "rockcrusher" M22 in the truck before my current. It's a tough transmission but I'd never run it on the streets because the ratios just suck! :rolleyes: The gears are so close together that you can literally shift from first to third (or second to fourth) and lose little acceleration. First gear was something like 2.20, I think.

The Muncie M21/M22 are high HP, low rear geared muscle-car transmissions. For a 235 I believe a Saginaw would be ideal. MUCH cheaper than the Muncies and better ratios.

-ftyler

Actually yes and no. Muncies or Saginaws were the choices for manual shift cars in the 60's and 70's. Not all of them were muscle cars. Many of them were 283's, 302's, 327's, and 350's. And because of the 1:1 final drive ratios, you got your cruising rpm by having a tall rear end, oftentimes a 3.08, but sometimes a 3.36.

Usually, the small blocks, because of their lower bottom end torque, got the "wide ratio" M20 muncie, which had a 2.52:1 first gear ratio. That's not as good as later overdrive transmissions, but better than the 2.20 1st that appeared in the M21 "close ratio" and M22 "rock crusher" transmissions.

If the motor was a muscle motor and had the balls for the 2.20 1st gear, the close ratio was highly desired (especially for SCCA racing) because the gears were split evenly so that a minimum of torque was lost between shifts. But yeah, that 2.20 is a big first step!

I think the reason the Muncies go for a lot of money is because they are such good transmissions. Even the M20 and M21 could handle something like 460 lb-ft if your tires don't slip. What made the M22 so much stronger was the straighter cut gears that caused less side deflection. But that also made it noisier.

However, long story short, I think you'll be happier using a T5 with it's steep first gear on a straight 6 engine. You've really got to have a lot of low-end balls to make a 2.20 1st gear feel decent.

I disagree in regards to that last post, about the M-21 or M-22 being such a good transmission they are not that good at all.
A few people have told me that the cases on those aluminum transmissions have a tendency to bust or crack easy, they are just a thin aluminum case.
I personally don't understand why they sell for so much money, the cheapest M-22 or M-21 I heard about that sold went for $350.00 and even that is too much those units don't even come with overdrive so your not saving any fuel with them.
However its possible to add overdrive it's available on them now but again it's not worth it, one guy told me that they run about $1800.00 to add on.

Okay. Well, I run an M21 behind a 427 big block in my Corvette making a minimum of 530 horsepower and it works well. I should be running an M22, but I run what I've got until I can afford better.

A friend of mine ran a wide ratio M20 behind a supercharged 327, and later, a supercharged 350 in his 68 Camaro and it worked fine.

Neither one of us has experienced a cracked case. So do you listen to what somebody has told you, or do you listen to experience?

I am in agreement that the Muncie is probably not the best choice for a straight-6 engine because the gear ratios aren't suited for something without 350 lb-ft or more of torque.
But really, Muncies have been and are still used very widely in muscle cars that make a lot more power than the factory provided originally, and you just don't see these things blowing up like many of the overdrive transmissions are.

If they had such a nasty reputation, they wouldn't be priced so high, nor have such a following among the faithful.
But you're entitled to your opinion. Just setting the record straight.

Well this guy that I was talking to one night at his house was using 3 of those M-22 rockcrusher units behind big block chevys he showed me what he had, and he has owned Chevy muscle cars for years and years this individual was not some bozo I had just meet at a flee market telling me some fiction storys.

So YES I do listen to experianced credible people when they tell me that the cases on those wonderful M-22 transmissions crack, therefore there not so great to have to pay an inflated price to own them in the first place, I would believe that.

Maybe your the type of guy who babys your vehicles and you might be using them in a nice way like the factory intended, meaning you drive your muscle cars nice and smooth and slow like say an older retired person would?, under those conditions that M-22 transmission would stand up ok and not break or crack the cases.

Now it might be that the T-10 is a better stronger sports car transmission, one guy I was talking to who is also very credible who owns a auto customizing repair shop says that some of the T-10 units rebuilt sell for more then a rebuilt muncie rockcrusher does, I would look into that first.

I do know that the muncie car transmissions in general are overvalued for what they are, they should only cost used $200.00 if that, period.

"Baby my muscle cars"...uh...no. That doesn't sound like me. I don't baby any of my cars. I drive them hard and maintain them well.

Not to argue, but it sounds like you listened to one guy, which isn't "listening to people with credible experience". Listening to "people" would mean more than one guy.

I'm not saying cracking doesn't occur, it does. If he has an engine that puts out enough poop to cause that kind of side deflection on the gears, then yes, an M22 can crack. But the good news is, stronger than OEM cases are now available, so all he had to do was buy an improved, re-engineered case and rebuild one of his M22's and he'd still be racing on it today.

The reason I'm sure my M21 is still alive is because I'm not running slicks and I'm not drag racing it. That puts a LOT of additional stress on any transmission.

You have now officially heard from someone else that has "credible" experience.

68 Corvette 427
68 Firebird 455
86 IROC-Z with Corvette 350
86 Shelby Charger with Lotus intercooled turbo motor

ChevyVan77, could you possibly do me a favor and ask your friend if he wants to sell one of his M22 Muncies? Preferrably one that doesn't have a bunch of fragged gears. And what would his price be? If the price is right, I can turn around and rebuild that M22 into one of those new Muncie cases and have a Rock Crusher for a decent price.

To be honest with you, the M22's I see at the swap meets usually go for anywhere between a grand and $1200 and I DO think that's a little too much. I'd love to have one though, and I would build it with a stronger case and a Gear Vendors overdrive unit on the back of it.

But really, many people do drive around with Muncies because there just haven't been THAT many options for stick shift Chevys in past years. Only now, the T56 6 speed double overdrives are starting to hit the swap meets, but they go for around $1400 and are rated at only 440 lb-ft, which is a lot less than what an M22 is rated for.

I do think your friend might have gotten ahold of some pretty tired M22s that perhaps were ready for a complete rebuild, either that or perhaps he runs some pretty gnarly big blocks with slicks, hitting it hard on the weekends at the dragstrip. But a lot of people drive Muncies of lesser reputation and don't have such problems with cracked cases.

You might want to talk to a transmission shop perhaps and get the opinions of some of the older professionals that have worked on a lot of Muncies.
Or...just buy a T10. But you know the Richmond T10 is really just a Muncie, they bought the rights to produce them. And the Richmond 5-speed is nothing more than a Doug Nash Muncie.
They're all just rebadged.

I guess I'll toss my two-cents in this Saginaw vs. Muncie discussion.

While I've never broken a Saginaw and have broken a Muncie, if I planned to abuse a transmission there is no question in my mind that I'd choose the Muncie.

I also think its unlikely a 235 would challenge either, so from that standpoint it makes little difference. However, I've never seen a shifter designed for the Muncie in a AD truck and on that basis I'd choose the Saginaw and the shifter that Patrick's offers.

Yes, that's true. That's my point too. I don't really know why we're arguing about whether or not a Muncie can stand up to big block abuse when the original thread was whether one could put a Muncie behind a 235. :confused:

Anyhow, in case anyone's interested, here is a site that sells Muncie parts, including STRONGER cases...

http://www.5speeds.com/store/html/4speeds.html

let me add my experience,I used to drag a 69 Chevelle 396 with a Muncie,never broke the tranny. back in the day,that's all ya had behind big block GM cars even guys running in the 11 second range which was quick then.The Saginaw 4 spd isn't as strong, but many guys ran them with modified smallblocks.
Like ya say,a no issue behind a 235.In fact Leo Santucci used to run an all out drag race 261 Chevy,buzzed it up to 7000 rpm.He told me the strongest non streetable 261 can't produce more than 290 HP and 350 ft lbs of torque,so no worrys for a Saginaw behind any 235/261.

To your first post Hotrod I will say sure that response from you sounds reasonable.

On your next post, now don't get me wrong I don't have anything against using the muncie car transmission if I was putting it in a car, except the general price of them but sometimes deals happen if people need quick cash.
I am not into cars I only deal in GM trucks and vans like my name.
I just wanted to point out that you were wrong and that those transmissions are not as good as you said they were other then that you know your what your talking about.

I prefere to use the overdrive units myself personaly, and no I would not buy one of those improved cases as you suggested if mine broke, all that does is send the CEO of that scam company and his cohorts away to Mexico to enjoy a BIG vacation at your expence, so go ahead and pay them.

Nevertheless if someone wanted to sell me one of those muncies that we are talking about that is in good shape and not broke then I would still try to buy it for as low as possible maybe $200.00, then sell it to you for what you expected it was worth, say $1000.00 bucks.
And gear add on units will cost you a pile of $$$ but it sounds like your loaded with cash anyway so it should be no problem.

Many manual trans problems can be traced to alignment, shifter, and wear issues. Many a cracked trans case can be traced to the use of a solid rear trans mount along with solid motor mounts. Speaking from experiance, even the highest powered drag cars using such pieces require the use of a rubber trans mount even if solid motor mounts/plates are used. This does not apply to the Liberty/Lenco level of performance, but the average 8sec car uses a rubber mount. The Vega we set up with a Jeffco had no rear mount. Even a low powered motor can muck-up a trans if things are out of whack. Me? I'd take a Liberty crash box made from a Hemi 4spd if I was still racin...assuming I just got tired of using a transbrake 'glide:).

I'd buy those Muncies all day long at $200 each figuring I'd double my money on most of them.

:rolleyes:

Everything mechanical breaks, it's designed into them,
Scott

I have a slightly different perspective on the Muncie discussion. I run an M20 in my '70 SS 396 El Camino...the later Muncies ('70 on) had solved many of their case cracking problems...but they never fixed their shift linkage problems...if it wasn't for the Hurst aftermarket fix that trans would still be undriveable.

ya the front mounts brake but its because the mount bolts are loose not because there a weak transmission