# '74 GTO transmission questions



## CRoberts91 (Dec 9, 2008)

A good friend of mine just picked up a '74 GTO and he needs a new transmission. It originally came with a 3speed auto but he wants to swap it out with a 4speed manual. It will be me and him doing a lot of the work on this thing. From what i have read an Muncie M22 is the best fit and function for this model. correct? it has a 350 bored to a 360 so it needs to be able to handle a good bit of torque. what all will we need to do the swap? does anyone know of a good conversion kit or have any advice from past experience? any help is greatly appreciated. thanks.


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## Davids4Speeds (Dec 9, 2008)

*'74 GTO 4 Speed transmision*

A M22 might be a bit of overkill. You may want to consider a M20 (wide ratio) or M21 (close ratio) depending on the rear end gear ratio. The M20 is compatible with your 3 series gears and the M21 with 4.11 or 4.56 gears.If concerned about strenght you can use a HD Muncie (26 spline input/ 32 output). All the Muncies in 1971-74 were HD 26/32 spline. Another inexpensive upgrade would be a cast iron midplate. It stiffens the trans and minimizes flexing. A must for big blocks or high torque motors.
David
262-513-8331


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## CRoberts91 (Dec 9, 2008)

So a muncie m20 would bolt right into place in the '74 and withstand around 400hp and ft-lbs, is that right?


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## Rukee (Feb 8, 2007)

It's the same tranny they used for the Tri-Power cars so I don't see why not. You'll need the pedal assembly and Z-bar with the rods, a flywheel and clutch assembly, a pilot bearing installed in the back of the crank, bell housing with the pivot ball and clutch release fork, the shifter and inside floor hump and the seal there..... prolly some other stuff too, just having a brain fart right now. :willy:


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## geeteeohguy (Feb 2, 2008)

The hardest thing to locate is gonna be the 4 speed console!!! 

Jeff


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## CRoberts91 (Dec 9, 2008)

mother mary thats a lot of stuff.  looks like we got some shoppin to do. well, thanks for the info guys. we'll be sure to post some pics once we get her runnin.


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## Too Many Projects (Nov 15, 2008)

CRoberts91 said:


> mother mary thats a lot of stuff.  looks like we got some shoppin to do. well, thanks for the info guys. we'll be sure to post some pics once we get her runnin.


IF you could find a wrecked or junked car with the pedals, linkage, console, it would be a HUGE advantage over trying to piece all this together from separate sources plus a visual help for where they all go in the car. There are many articles on the web about this conversion to read and see what's involved. Do a google for gm auto to 4 speed swap and see what you get.

Another option to consider might be to move into a later setup with a hydraulic clutch release. IF that would convert easily into the 74, you would eliminate piercing the firewall for the clutch rod and the need for the whole frame bracket, Z-bar, engine mounted mechanical linkage. I'm not savvy to whether the bell housings will interchange to do this swap, but it would be worth exploring.


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## CRoberts91 (Dec 9, 2008)

i have been looking for kits and all kinds of stuff, but it seems everything stops at '72. whats the deal? why are the '74 parts so hard to find?


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## Too Many Projects (Nov 15, 2008)

CRoberts91 said:


> i have been looking for kits and all kinds of stuff, but it seems everything stops at '72. whats the deal? why are the '74 parts so hard to find?


GM quit building performance cars after 72 and just put automatics in everything.........


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## Rukee (Feb 8, 2007)

I'm thinking `72 clutch linkage parts/pedals will fit in your `74.


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## Too Many Projects (Nov 15, 2008)

Rukee said:


> I'm thinking `72 clutch linkage parts/pedals will fit in your `74.


That may be the only option. I was surfing car-part.com and google for clutch parts for a 74 LeMans/GTO and they don't seem to exist.........:confused
I was only joking about the performance parts ending in 72, but I may have been more right than I knew....
What other GM model would've been the same for 74? The Malibu shrank in size but may still share drivetrain components. Maybe that would work. 
Anyone have access to a Hollander Interchange for 74 ? That would be a good place to start.


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