[Steve67L-79]

I have just finished my 67 L79 clone project and wonder if my M20 will hold in the long haul. I have rebuilt my 327 to a 383 with about 500 HP and 500 ft/lbs torque, that is if one can believe the comp cams program that I used when I selected my cam. My concern is for the M20. I would prefer to be proactive in protecting the transmission, rather than have to do major repairs down the road. I am running 3.31s in the rear with 295-50-15s. I am thinking of moving up to some sort of drag radial for better traction. What can I do to the Muncie to ensure it to have a long life, so that it can stand a steady diet of power shifting, etc? I really want to keep the Muncie as all I read says that aftermarket transmissions will likely not shift like my Muncie. Any input greatly appreciated.

 

[Mr Chevelle]

The best solution would be to give me your old Chevelle. I already have lots of your old parts on my car. TD would feel right at home in my garage next to the parts...and....YOU wouldn't have to worry about the tranny ever again...............:waving:

Beautiful car Steve..............

 

[Steve67L-79]

Thanks Pat, I could do as you suggest, but it is a hardtop car and we both know how you feel about them.

 

[Mr Chevelle]

I would definitely make an exception in this case..........

 

[how69ss]

I would swap the case out for a supercase and nodular iron mid plate. You can get these from auto gear or from Wally.

This is what I did. I run mine pretty hard, though I've still got some big tire spin at the track. I have over a 100 runs on mine since it was rebuilt. Car runs in the 7.90s 1/8 mile or what would be a 12.40 1/4 about at 5800 DA. I slam through the gears pretty good, and have lifted the front tire a few times this season.

I plan to hook hard next season with full slicks, so we will see how it holds up. Should be fun. My motor made 543 tq on the engine dyno, so in the car and uncorrected it's probably 475-500. All steel, full weight 69.

I ran drag radials,etc, for years, and slicks too, and I never damaged mine, even with 130,000+ miles and before it was rebuild. It all depends on how hard you hook up. For street driving, I'd just get a standard rebuild kit with counter shaft from wally, a supercase and the nodular iron midplate.

Make sure that you have someone rebuild it that really knows what they are doing, too.

 

[JodysTransmissions]

how69ss has a great plan for you, also swap out the M20 gearset and use the M22W with the 2.56:1 1st.

 

[Rich-L79]

how69ss has a great plan for you, also swap out the M20 gearset and use the M22W with the 2.56:1 1st.

At that point it would seem easier to just buy an AutoGear M22W and put the old Muncie in storage. It would be a whole lot less fuss to just swap transmissions.

 

[how69ss]

Supercase-265.00
rebuild kit- 180.00
iron midplate 60.00

If you need to replace 1st and 2nd gear, 170.00. Which you may not need to do.

Without the gears, that's $505.00. Cost me under $300 for labor, I think, but I am sure that varies depending on where you are at.

So that's $800 total.

The M22W is $1950.00 and you'd have to use a different clutch. Think it has a 26 spline input shaft rather than 10 spline which is what an M20 has for 1966-1970.

http://www.5speeds.com/muncie2.htm

 

[how69ss]

The M20 has a 2.52 first gear.

 

[JodysTransmissions]

The M22W is also available with a 10 spline input/maindrive gear.

 

[how69ss]

The M22W is also available with a 10 spline input/maindrive gear.

That's good to know. I might eventually get one and use my m20 for backup.

Can you get the same spline output shaft for it as comes with the M20? Mine has a 27 spline output and the M22 and came with a 32 spline output shaft, right?

 

[JodysTransmissions]

As a custom builder, any spline count combo can be built to utilize existing parts.

Possible spline combos:
10/27
10/32
26/27
26/32

 

[how69ss]

Great. That was one of my worries for when I switch to a different clutch and spend some $$$, being able to upgrade to a different Muncie, like the M22W but still use the same clutch and driveshaft, etc.

What do you think is the ball park torque capacity for the M22W in an all steel, iron headed, full weight chevelle running slicks?

 

[how69ss]

I have just finished my 67 L79 clone project and wonder if my M20 will hold in the long haul. I have rebuilt my 327 to a 383 with about 500 HP and 500 ft/lbs torque, that is if one can believe the comp cams program that I used when I selected my cam. My concern is for the M20. I would prefer to be proactive in protecting the transmission, rather than have to do major repairs down the road. I am running 3.31s in the rear with 295-50-15s. I am thinking of moving up to some sort of drag radial for better traction. What can I do to the Muncie to ensure it to have a long life, so that it can stand a steady diet of power shifting, etc? I really want to keep the Muncie as all I read says that aftermarket transmissions will likely not shift like my Muncie. Any input greatly appreciated.

Can you describe your motor in detail? That's pretty healthy if it makes that much power. Must have really good heads, roller cam or aggressive solid flat tappet?

 

[1966_L78]

Supercase-265.00
rebuild kit- 180.00
iron midplate 60.00

If you need to replace 1st and 2nd gear, 170.00. Without the gears, that's $505.00. Cost me under $300 for labor, I think, but I am sure that varies depending on where you are at.

So that's $800 total. ~1000 with gears...

The M22W is $1950.00
http://www.5speeds.com/muncie2.htm

$800 versus ~$2000, not to mention any other used pieces you might need to replace (as mentioned, 1st/2nd is another $170, and shift forks, etc...

IF the M20 isn't original to the car, but nice shape, you could probably sell it for ~$500, to help offset the extra cost of the NEW trans...

 

[kettbo]

I have had my M-20 in my 68 RatVette for over 15 summers. I romp on it but am an adult, not doing kid things like donuts...... 427, roughly 450 horse.....
M-20s are not THAT weak

 

[Rich-L79]

M-20s are not THAT weak

That really is true. I recently had the M20 out of the L79 car to chase down a few leaks. The last time anyone was inside this trans was about 1984! While the L79 is stock and a 327 hardly puts out the torque of a 427, this car was driven HARD for the 138,000 miles prior to my getting it. I too have given it a few shots at the track and have run a few times with slicks. I can report, the inside of the transmission looks great and the cross shaft is still solidly planted in the case. I am replacing the shift forks, but what do you expect for nearly 150,000 of hard use?

ANYTHING will break if you abuse it enough or combine abuse with being stupid. That said, for a high power street car which will see some abuse and/or track use, an Auto Gear "Muncie" will always be stronger than its original Muncie counterpart.

 

[Steve67L-79]

Okay, this is sounding like what I think I am after. What would the torque rating on the M22W be, at least approximately? If I decide to spring for it I want to make certain that it will help me avoid tearing it up.

 

[JodysTransmissions]

Great. That was one of my worries for when I switch to a different clutch and spend some $$$, being able to upgrade to a different Muncie, like the M22W but still use the same clutch and driveshaft, etc.

What do you think is the ball park torque capacity for the M22W in an all steel, iron headed, full weight chevelle running slicks?

George will not torque rate any of his gearsets but, I have M22W's out there behind 500 -600 hp vehicles without any breakage.

$800 versus ~$2000, not to mention any other used pieces you might need to replace (as mentioned, 1st/2nd is another $170, and shift forks, etc...

IF the M20 isn't original to the car, but nice shape, you could probably sell it for ~$500, to help offset the extra cost of the NEW trans...

This is a great solution for off setting the price, once you have a properly built M22W you won't need a back-up trans.

Okay, this is sounding like what I think I am after. What would the torque rating on the M22W be, at least approximately? If I decide to spring for it I want to make certain that it will help me avoid tearing it up.

I repair Jerico's and G-Force drag race transmissions, nothing will hold up to abuse! But, the M22W will take more abuse than an M20.

 

[how69ss]

George will not torque rate any of his gearsets but, I have M22W's out there behind 500 -600 hp vehicles without any breakage.



This is a great solution for off setting the price, once you have a properly built M22W you won't need a back-up trans.



I repair Jerico's and G-Force drag race transmissions, nothing will hold up to abuse! But, the M22W will take more abuse than an M20.

I will be able to give you a pretty good idea for the M20 with supercase and how it holds up to abuse by the end of next summer. I am going to run it VERY hard.

I agree, with racing it's not really a question of IF something is going to break, it's just a question of WHEN.