Manual trans conversion

[Bentley]

Muncie M-20 - wide ratio 4 speed (2.52 1st)
Muncie M-21 - close ratio (2.20 1st)
Muncie M-22 - close ratio (2.20 1st) heavy duty aka Rockcrusher

They were more rare than people think and were usually speced on the high hp big block cars

These are the correct transmission designations... Of all of the cars I was around (early/mid 70's) I NEVER saw a M22 rockcrusher, the were very rare.. I had a 69 Dodge Super Bee A12 car as a Jr/Sr in High School ( 72/73) It had the Hemi 4 speed in it and I remember the noise it made, comparing it to the M22.

I am embarrassed to tell this story, but one night 3 of us were in it, smoking some bud, and one of us had brought a tape recorder ( probably one of the " new "cassette ones..LOL) The transmission noise dominated the entire tape, beside when the "six pack" came on....

I am dinking around now with a Fox body ( I inherited it from my sons estate) and what I don't understand is if you are going to spend that much money why are you not looking at the new Tremec TKX???? I am considering replacing the 4 speed SROD in the mustang and IF I want to spend more money than the car is worth, this is what I am going to do

 

[carhead22000]

Hi biker
With my rear gears, not sure what this will drive like with an s10. They are though much easier to find. I must admit I'm coming around to not doing the trans and just put new seals in his automatic for now. I think it will be a lot of work just to find he doesn't like the ratio.
Will look for a civic

get a 350 turbo auto and put a good hard shift kit in it.he will like that just the same when it shifts chirpin the tires.

 

[DesmoEd]

My '69 vette was originally an L46 car (350ci/350hp). The original motor was long gone when I got it but it still had its original close ratio M-21 and 3:73 rear axle. The 2:20 1st gear was ok behind the mild 350 that was in the vette when I bought it but at a bare minimum 3:73 was necessary out back - and this is in a car that's a lot lighter than a 2nd gen Camaro.

I went from TH350 to M-20 to TKO600 over the past 10 yrs in my '73 Camaro. I'm a KISS proponent so I stayed with the mechanical clutch linkage and this also helps keep cost down. When I swapped TH350 for the M-20 I considered going with a TKO 600 at that time as I already had one in the vette and loved it but I got a smokin deal on a fully rebuilt M-20 so I decided to go with the 4 speed estimating an additional $1500 to swap in a TKO instead. I went with the M-20 for its 2.52 1st gear and had originally planned to fit 3:42 gears out back for better cruise but after initially driving the car I quickly decided that was not gonna work well with the engine combo I have.


Some of the later BW ST-10's had a better 2.64 1st gear. Paired with a mild engine/cam setup that makes decent tq off idle, that may very well make a good street combo.

 

[Zspoiler]

The aftermarket ones have a 2:88 1st gear available. When I converted my 1979 Z-28 from a Turbo 350 to a M-21 Muncie to a Super T-10 .I kept my 3:42 gears even when a started with my stock LM-1 and to my custom supercharged 377 small block.Because its more of a street car than a race car.With a lot of custom touches.Even though there are a lot more 5 and 6 speeds available now.

 

[Postmech]

My car (78) came with a 3.73 and BW aluminum case 2.64 geared T10 with GR70-15 tires. Later went to a Richmond 5 speed and 2.93 gears and 245 50r16 tires. Now has mild 383 with TKO 500 with 2.93 gears and 235 65r16 tires. Much better now. Its all in the combination , the cruise RPM needs to match camshaft and engine size. More low end torque, less gear needed.

 

[DesmoEd]

The aftermarket ones have a 2:88 1st gear available. When I converted my 1979 Z-28 from a Turbo 350 to a M-21 Muncie to a Super T-10 .I kept my 3:42 gears even when a started with my stock LM-1 and to my custom supercharged 377 small block.Because its more of a street car than a race car.With a lot of custom touches.Even though there are a lot more 5 and 6 speeds available now.

I really wanted to run 3:42 out back behind the M-20 as I thought it would be a good combo but cam choice dictated otherwise.

I had a 10-1 hyd roller 355 built for my '73 about 10 yrs ago. Again, it was a TH350 car back then, so we speced the Comp XR270HR (218/224@.50) for excellent midrange and torque. It was an excellent combo - 16 in vacuum @850 rpm and tons of low end. Never really liked auto tranny muscle cars but my wife was supposed to drive it occasionally so the TH350 stayed. After ~1000 miles my wife had yet to drive the car and I had reliability issues with the TH350 so it came out and the stick went in.

Pulled the motor along with the tranny and sent it back to the builder for more cam to suit the manual tranny. Howard's 224/230@.050 went in and it really opened up the top end but as expected what I gained above 5000rpm I lost below 3000...and that quickly killed any notion of running 3:42 out back.

Ultimately, being stuck with 3:73 out back killed the 4 speed for me. I pulled it and sold it along with the shifter and clutch for not much less than I paid....

Finally ended up with a .64 OD TKO600 in my Camaro, great transmission just be careful when selecting ratios and make sure you are taking into account cam profile, tire size, and induction type. The .64 OD was a little deep for me with 3:73 out back - I just had the rear end rebuilt and went with 4.10 gears which I really like for my setup.

 

[XLR8]

Mine is an M22 "Wide Ratio" with a dual disk McCloud clutch. Not sure what first gear is, but with my 272 limited slip rear gears it is fine to get me to 2nd where all hell breaks loose to get me to 3rd, with the high rear gears you have to get up into speed to get it all working together. It surprises people to be going about 70 in 4th then down shift to 3rd and take off, especially sport bikes. Love it. Rev limiter set at 6,500 to be safe.

 

[Zspoiler]

I tried to find a decent 4 speed 2nd gen Camaro (My brother had a 1972 SS) So I kept the M-21 and clutch and bell set up from my 1973 Nova SSHB.And got the clutch linkage from Chevrolet .And built my own .And have been satisfied ever since.

 

[G72Zed]

Finally ended up with a .64 OD TKO600 in my Camaro, great transmission just be careful when selecting ratios and make sure you are taking into account cam profile, tire size, and induction type. The .64 OD was a little deep for me with 3:73 out back - I just had the rear end rebuilt and went with 4.10 gears which I really like for my setup.

This quote is bang on the money and absolutely critical.

I have driven some real nice manual muscle cars & hot rods over the years, some owners did not do the homework first, some even just went with what some companies told them to buy. Big purchase to get wrong.

I have found that a little too much gear was not as bad as not enough.

Like DesmoEd, I was not about to change the rear gears (3.73) and found the .64 too much of a drop % wise, and the .82 not enough for the fast highway speeds. Took the money for a gear swap and went with the Tremec TR6060, got both choices, .80 and .63. I like a 2.7 to 2.9 final drive and the 11 to 1 first is great fun LOL.

 

[CT1275]

This quote is bang on the money and absolutely critical.

I have driven some real nice manual muscle cars & hot rods over the years, some owners did not do the homework first, some even just went with what some companies told them to buy. Big purchase to get wrong.

I have found that a little too much gear was not as bad as not enough.

Like DesmoEd, I was not about to change the rear gears (3.73) and found the .64 too much of a drop % wise, and the .82 not enough for the fast highway speeds. Took the money for a gear swap and went with the Tremec TR6060, got both choices, .80 and .63. I like a 2.7 to 2.9 final drive and the 11 to 1 first is great fun LOL.

What do you think about a .77 OD gear with 3.73 or 3.42 rear gear? I'm considering a Richmond 5 speed with 5th gear OD.
Also am curious if 1st through 4th, or whatever the 1:1 gear would be on any trans, why is the OD so critical? I would think taller gear the better for highway cruising? A lot of guys swear by swapping to a T56 6 speed, even the one with .50 6th gear and 3.73 rear gear. I think other versions are .63. So just curious on that. What are issues that come from this?