Jeff----
Well now, someone's finally posted a subject that I really know something about----Muncie transmissions.
First of all, Alex is absolutely correct; your 72 Muncie transmission is more than adequate to handle anything that your modified small block can throw at it. For transmissions, the most important strength attribute is TORQUE handling capacity, not raw horsepower. A 1970 Muncie M-21, which is not as strong as your '72(more later on why), could handle the 500 lb/ft output of the LS-5 454, the highest TORQUE output ever installed in a Corvette. I hardly think your small block will approach the 500 lb/ft figure no matter what you do to it unless you're talking about a race-only configuration.
Without getting into fine details and special applications, there were several different versions of the Muncie transmission produced over the years of production from 1963 through 1974. The first version, produced only as M-20, was manufactured from 1963 through 1965. This is the weakest Muncie. It had a 7/8" countergear shaft, a 10 spline input shaft, and a 26 spline output shaft. The second version, produced as M-20, M-21, and M-22, was manufactured from 1966 until 1970. It was stronger with a 1" countergear shaft, but still used a 10 spline input and a 26 spline output. There were several minor variations produced during this transmissions life. For 1971 through 1974, the Muncie transmission was revised again for all variants, M-20, M-21, and M-22. The 71-74 Muncie used the 1" countergear shaft, but used a stronger 26 spline input shaft and a different mainshaft, GM #3978759, with considerably larger output shaft of 32 spline configuration.
As far as M-22s go, I can tell you this: In 1985 I purchased all of the GM parts, save one, to build a "second design" 66-70 Muncie M-22 transmission. Even at that time, several of the parts had been discontinued and I had to scour the country to find and purchase NOS examples. I was successful with the exception of the rear bearing retainer plate, GM # 3831752, which proved a daunting task to locate. Anyway, at that time, having paid wholesale prices for the parts that were still available and "asking price" for the NOS pieces, the parts cost me over $3,000. And I still didn't have the NOS bearing retainer plate. I found that about a year ago, paid $300 it and assembled the transmission.
As far as $3,800 goes for an assembled complete, "new", M-22 transmission, I think that's a GREAT price. A GREAT price IF it is assembled from all new GM components. I seriously doubt that this is the case. If you check, I think that you will find that it will be assembled from mostly REPRODUCTION new pieces and some used pieces. A properly "dated" NOS main case for your trans would be virtually impossible to find. I know for sure that an NOS rear bearing retainer plate will be difficult----it took me 12 years to find one. Reproduction gears for Muncie transmissions, including M-22 gears, are being manufactured. However, I seriously doubt that they are cut from the same, special, high nickel alloy steel as the originals were. Maybe, though.
Well now, someone's finally posted a subject that I really know something about----Muncie transmissions.
First of all, Alex is absolutely correct; your 72 Muncie transmission is more than adequate to handle anything that your modified small block can throw at it. For transmissions, the most important strength attribute is TORQUE handling capacity, not raw horsepower. A 1970 Muncie M-21, which is not as strong as your '72(more later on why), could handle the 500 lb/ft output of the LS-5 454, the highest TORQUE output ever installed in a Corvette. I hardly think your small block will approach the 500 lb/ft figure no matter what you do to it unless you're talking about a race-only configuration.
Without getting into fine details and special applications, there were several different versions of the Muncie transmission produced over the years of production from 1963 through 1974. The first version, produced only as M-20, was manufactured from 1963 through 1965. This is the weakest Muncie. It had a 7/8" countergear shaft, a 10 spline input shaft, and a 26 spline output shaft. The second version, produced as M-20, M-21, and M-22, was manufactured from 1966 until 1970. It was stronger with a 1" countergear shaft, but still used a 10 spline input and a 26 spline output. There were several minor variations produced during this transmissions life. For 1971 through 1974, the Muncie transmission was revised again for all variants, M-20, M-21, and M-22. The 71-74 Muncie used the 1" countergear shaft, but used a stronger 26 spline input shaft and a different mainshaft, GM #3978759, with considerably larger output shaft of 32 spline configuration.
As far as M-22s go, I can tell you this: In 1985 I purchased all of the GM parts, save one, to build a "second design" 66-70 Muncie M-22 transmission. Even at that time, several of the parts had been discontinued and I had to scour the country to find and purchase NOS examples. I was successful with the exception of the rear bearing retainer plate, GM # 3831752, which proved a daunting task to locate. Anyway, at that time, having paid wholesale prices for the parts that were still available and "asking price" for the NOS pieces, the parts cost me over $3,000. And I still didn't have the NOS bearing retainer plate. I found that about a year ago, paid $300 it and assembled the transmission.
As far as $3,800 goes for an assembled complete, "new", M-22 transmission, I think that's a GREAT price. A GREAT price IF it is assembled from all new GM components. I seriously doubt that this is the case. If you check, I think that you will find that it will be assembled from mostly REPRODUCTION new pieces and some used pieces. A properly "dated" NOS main case for your trans would be virtually impossible to find. I know for sure that an NOS rear bearing retainer plate will be difficult----it took me 12 years to find one. Reproduction gears for Muncie transmissions, including M-22 gears, are being manufactured. However, I seriously doubt that they are cut from the same, special, high nickel alloy steel as the originals were. Maybe, though.
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