M20 or M22 transmission length
Thread Starter
Instructor
Joined: Jan 2011
Posts: 102
Likes: 1
From: St. Jacob IL
M20 or M22 transmission length
My brother in law is doing a T56 swap on his '68. He has offered me one of two transmissions he has in the car: either the M22 that's in the car or an M20 wide ratio that he has as a spare. The deal will include the bell housing, clutch, flywheel and linkages. I will buy a new spring and plate, have the flywheel resurfaced and will rebuild whichever Trans I get.
My '80 currently has a TH350 with 3.73 rear end gears. I am leaning towards the M20 to give me a better too end and my motor makes ~420 at the crank so I doubt I will miss the lower gearing. If anyone disagrees please tell me.
My question is, how long are the Muncies compared to my Turbo? Will I have to have my drive shaft shortened or have a new one cut?
My '80 currently has a TH350 with 3.73 rear end gears. I am leaning towards the M20 to give me a better too end and my motor makes ~420 at the crank so I doubt I will miss the lower gearing. If anyone disagrees please tell me.
My question is, how long are the Muncies compared to my Turbo? Will I have to have my drive shaft shortened or have a new one cut?
Drifting
Joined: May 2005
Posts: 1,968
Likes: 44
From: East TN
I did a T56 swap on my 1980 4 speed and still have the original trans crossmember and driveshaft sitting in my garage. The driveshaft has the slip yoke with solid Spicer U joints and the crossmember was acid dipped and powdercoated red. If it turns out that they are something you need, PM me. 
Safety Car
Joined: Sep 2007
Posts: 4,458
Likes: 331
From: Indy Indiana
neither transmission will give you a better top end, 4th gear is straight thru and 1:1 ratio on both of them.
the m20 with it's lower 1st gear ( higher numerically ) will give you better torque multiplication in 1st gear.. the m22 will have 2nd and third gear closer together. you won't see as much rpm difference between gears.
the m20 with it's lower 1st gear ( higher numerically ) will give you better torque multiplication in 1st gear.. the m22 will have 2nd and third gear closer together. you won't see as much rpm difference between gears.
Thread Starter
Instructor
Joined: Jan 2011
Posts: 102
Likes: 1
From: St. Jacob IL
Thanks guys. I knew about the 1:1 final drive. For some reason the way I was thinking about it I was operating under the impression that the M22 had some sort of underdrive final gear, even though I knew it didn't. 
Easy Mike, that is a good idea.
Mike80, so I am correct in assuming then that the Muncies will NOT bolt up to my TH30 crossmember? Will I have problems mounting the other crossmember since my car is set up for a bolt on xmember and the manuals were weld-on? I might very well take you up on that offer. PM sent your way.
Easy Mike, that is a good idea.
Mike80, so I am correct in assuming then that the Muncies will NOT bolt up to my TH30 crossmember? Will I have problems mounting the other crossmember since my car is set up for a bolt on xmember and the manuals were weld-on? I might very well take you up on that offer. PM sent your way.
Racer
Joined: Feb 2012
Posts: 421
Likes: 27
From: Harrisburg PA
As far as your original question, I could be wrong, but my research so far indicates that a Muncie will be a direct bolt in replacement for the TH350...at least as far as size goes...
same cross member, same drive shaft, etc...
I can tell you, form experience with my other car on which I did the swap, that was the case--I do not see why it would be any different on the 'vette, either--the dimensions of the Muncie and TH350 do not change
same cross member, same drive shaft, etc...
I can tell you, form experience with my other car on which I did the swap, that was the case--I do not see why it would be any different on the 'vette, either--the dimensions of the Muncie and TH350 do not change
Last edited by keithl1967; Mar 6, 2014 at 07:14 PM.
Racer
Joined: Feb 2012
Posts: 421
Likes: 27
From: Harrisburg PA
yes, including bellhousing, from back of engine to back of transmission, the tH350 is the same length as a muncie...
assuming it is a car TH350, and not a truck TH350 that has the long tailhousing...
assuming it is a car TH350, and not a truck TH350 that has the long tailhousing...
Last edited by keithl1967; Mar 8, 2014 at 11:57 AM.
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Heel & Toe
Joined: Aug 2012
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M20/M22 vs TH350
In fact, the M20 with GM bell housing is a direct fit to the TH350, same lenght, output shaft splines count. A M22 shares same dimention lenght wise but output slines count is 32 like a TH400.
Hope this helped !
Hope this helped !
Thread Starter
Instructor
Joined: Jan 2011
Posts: 102
Likes: 1
From: St. Jacob IL
It did! So the M20 would be a more direct fit. The motor was designed based on the TH350 that is in the car. I do not believe that it is a truck 350. The cam on the motor gives me a very wide power band (~1500 - 5500, redlining at 6500). Would the wide ratio be the better choice for me then?
Racer
Joined: Feb 2012
Posts: 421
Likes: 27
From: Harrisburg PA
It did! So the M20 would be a more direct fit. The motor was designed based on the TH350 that is in the car. I do not believe that it is a truck 350. The cam on the motor gives me a very wide power band (~1500 - 5500, redlining at 6500). Would the wide ratio be the better choice for me then?
As far as which would be better for you, it really depends on the rear gear you have. If you have the stock 3.08, I would go with the M20, which has a more stout 2.56 (or 2.52, depending upon the year of the trans) first gear (the M21 is a 2.20, if memory serves correctly). This means, you will have abetter "launch" off the line with the M20 and a stock gear.
If your rear is NUMERICALLY higher than 3.73 (ie 3.90 or 4.11), I would go with the M21...
In my '67 camaro, I have an M20 and a 3.73...it is really the "sweet spot" for taking off, but 1st gear is VERY short lived before having to shift...
Last edited by keithl1967; Mar 12, 2014 at 08:21 AM.
Racer
Joined: Feb 2012
Posts: 421
Likes: 27
From: Harrisburg PA
If the gear is numerically higher than 3.73 (ie 3.90, 4.10), then I would go with the M21...
You could always put the rear of the car up in the air (properly supported, but so both rear wheels can turn freely), and mark the tire. Spin it forward, and count the number of revolutions of the pinion yoke for one full tire revolution...just over 3= 3.08; 3 and 3/4turns =3.73, closer to 4 full turns, and your looking at 3.90's or 4.10, etc...
Le Mans Master
Joined: May 2003
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From: Fernandina Beach FL
2023 Restomod of the Year finalist
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My brother in law is doing a T56 swap on his '68. He has offered me one of two transmissions he has in the car: either the M22 that's in the car or an M20 wide ratio that he has as a spare. The deal will include the bell housing, clutch, flywheel and linkages. I will buy a new spring and plate, have the flywheel resurfaced and will rebuild whichever Trans I get.
My '80 currently has a TH350 with 3.73 rear end gears. I am leaning towards the M20 to give me a better too end and my motor makes ~420 at the crank so I doubt I will miss the lower gearing. If anyone disagrees please tell me.
My question is, how long are the Muncies compared to my Turbo? Will I have to have my drive shaft shortened or have a new one cut?
My '80 currently has a TH350 with 3.73 rear end gears. I am leaning towards the M20 to give me a better too end and my motor makes ~420 at the crank so I doubt I will miss the lower gearing. If anyone disagrees please tell me.
My question is, how long are the Muncies compared to my Turbo? Will I have to have my drive shaft shortened or have a new one cut?
For clarification Muncies PRE 71 are ¾" SHORTER than the later ones....
Here's a good read- http://www.chevyhiperformance.com/te...swapping_tech/
Richard