Need 4spd decoded
Thread Starter
Pro
Joined: Nov 2004
Posts: 645
Likes: 0
From: Oregon
Okay, this is what I know so far... The trans is definatly a M-22, stamped housing numbers and letters bear this out. It is date coded Aug.28th 8/71, The production numbers on the car, and the d/s door it reads 9/71 along with matching production numbers. So the dates from the car to the trans work. There are NO other production numbers (from a different car) anywhere. This may prove that mistakes where made in My production numbers being absent. When the trans is pulled next week I will find out the number of splines. This set of conditions can only mean one of three things... One, this was a "special ordered car", two, the trans was a "fill in" to keep the line moving, the third it was used as a "warrenty replacement". This also explaines why this thing is SOOO LOUD (gear whine) in first and second gears!
Safety Car
Joined: Apr 2000
Posts: 3,802
Likes: 61
From: Wichita KS
Okay, this is what I know so far... The trans is definatly a M-22, stamped housing numbers and letters bear this out. It is date coded Aug.28th 8/71, The production numbers on the car, and the d/s door it reads 9/71 along with matching production numbers. So the dates from the car to the trans work. There are NO other production numbers (from a different car) anywhere. This may prove that mistakes where made in My production numbers being absent. When the trans is pulled next week I will find out the number of splines. This set of conditions can only mean one of three things... One, this was a "special ordered car", two, the trans was a "fill in" to keep the line moving, the third it was used as a "warrenty replacement". This also explaines why this thing is SOOO LOUD (gear whine) in first and second gears!
You car is 1972 model year car but the transmission is a 1971 model year transmission.
That August 28 date is for a 1970 build.
cc
Thread Starter
Pro
Joined: Nov 2004
Posts: 645
Likes: 0
From: Oregon
Okay, this is what I know so far... The trans is definatly a M-22, stamped housing numbers and letters bear this out. It is date coded Aug.28th 8/71, The production numbers on the car, and the d/s door it reads 9/71 along with matching production numbers. So the dates from the car to the trans work. There are NO other production numbers (from a different car) anywhere. This may prove that mistakes where made in My production numbers being absent. When the trans is pulled next week I will find out the number of splines. This set of conditions can only mean one of three things... One, this was a "special ordered car", two, the trans was a "fill in" to keep the line moving, the third it was used as a "warrenty replacement". This also explaines why this thing is SOOO LOUD (gear whine) in first and second gears!
Racer
Joined: Feb 2007
Posts: 273
Likes: 0
From: NAPLES FLORIDA
Don't forget that in the date code on a transmission, the year is not the year the transmission was built but the model year of the car it's going into.
You car is 1972 model year car but the transmission is a 1971 model year transmission.
That August 28 date is for a 1970 build.
cc
You car is 1972 model year car but the transmission is a 1971 model year transmission.
That August 28 date is for a 1970 build.
cc
Le Mans Master
Joined: Dec 2003
Posts: 5,727
Likes: 38
From: Fremont CA
My only problem with this is the 10 spline input shaft. I have an early build August car and it has a 26 spline input shaft. It is a 72. The car was built the second week of August so the trans should have been built before yours and it is a 26 spline. Mine has my VIN number on the side of the trans also. This may have been swapped into the car. If the trans is truely built in August of 71 it should be a 26 spline input, unless this is a freak car which could be possible.
Safety Car
Joined: Apr 2000
Posts: 3,802
Likes: 61
From: Wichita KS
Not necessarily true in my experience...I have a (1973 stamped) M-20 transmission in my 1974 LS4 convertible. The car was built the 5th of November 1973 and is car #8167 of the assembly line (which is an early build) but not so early as to explain why I have a "3" stamped where a "4" should be on my "numbers matching" original transmission! See pic...
My answer still applies since the OP's car is a 1972.
cc
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Melting Slicks
Joined: Mar 2005
Posts: 2,093
Likes: 297
From: Midlothian VA
Based on your photos what you have is a M22 assembled for 1971 model year production (vette, chevelle, camaro).
Otherwise, your input/output shafts, main case casting number, output case casting number, side case casting number, assembly date stamping, and (would need closer photo but appears that) your drain plug being stamped with a "P" (all 70 & up had a drain plug but M22 is stamped P and is magnetic) are correct for a 1971 M22. Your casting date code on the main case appears to be missing or ground off.
The assembly model year and missing VIN is a killer for proving originality to your vehicle but at least you have a great gear box.
Note: only 20 M22's went into 1972 Corvette production for the ZR1.
Otherwise, your input/output shafts, main case casting number, output case casting number, side case casting number, assembly date stamping, and (would need closer photo but appears that) your drain plug being stamped with a "P" (all 70 & up had a drain plug but M22 is stamped P and is magnetic) are correct for a 1971 M22. Your casting date code on the main case appears to be missing or ground off.
The assembly model year and missing VIN is a killer for proving originality to your vehicle but at least you have a great gear box.
Note: only 20 M22's went into 1972 Corvette production for the ZR1.
Terrorizing Orange Cones
Joined: Oct 2007
Posts: 2,572
Likes: 17
From: Northern CO
Here's a comparison shot for GTPLUS2 and other interested parties of another base motor, 4-sp, '72 car.
As you can see, mine is date coded P2P28A (the first "P" and "A" strikes are light, possible causes: fonts wearing, tool not flat on strike) and with the partial VIN immediately above the trans ID:
More close up:
If the ID stamping process was consistent (partial VIN & trans date code location and orientation), then the OP's trans is not following protocol. Not to say it didn't come in that car but methinks, his M-22 has been swapped in from another GM product of earlier vintage.
That's my story and I'm stickin' to it.
As you can see, mine is date coded P2P28A (the first "P" and "A" strikes are light, possible causes: fonts wearing, tool not flat on strike) and with the partial VIN immediately above the trans ID:
More close up:
If the ID stamping process was consistent (partial VIN & trans date code location and orientation), then the OP's trans is not following protocol. Not to say it didn't come in that car but methinks, his M-22 has been swapped in from another GM product of earlier vintage.
That's my story and I'm stickin' to it.
Thread Starter
Pro
Joined: Nov 2004
Posts: 645
Likes: 0
From: Oregon
Wow! got it back today, the trans only needed an input shaft bearing and a few various o rings and gaskets. This M22 drives out sweet and smooth! As long as it was out I also opted for a new clutch pack as well. the numbers bear out that it was date stamped Aug. 28, 1971. The built tag on the D/S door say's 9/71, close enough for Me Guy's. This car is an original 94k car and has only had three owners (including me) I have been told that "mistakes" on the line have been found out about, and missing production numbers happened. I am impressed to hear that there where only "22" LT1's with the rockcrusher trans where ever made. My trans... and car... are dated in the same year and the same month... It's a match! Okay there are NO production numbers present, where they are suppost to be, perhaps this really make this a rare combination!
Melting Slicks
Joined: Mar 2005
Posts: 2,093
Likes: 297
From: Midlothian VA
Wow! got it back today, the trans only needed an input shaft bearing and a few various o rings and gaskets. This M22 drives out sweet and smooth! As long as it was out I also opted for a new clutch pack as well. the numbers bear out that it was date stamped Aug. 28, 1971. The built tag on the D/S door say's 9/71, close enough for Me Guy's. This car is an original 94k car and has only had three owners (including me) I have been told that "mistakes" on the line have been found out about, and missing production numbers happened. I am impressed to hear that there where only "22" LT1's with the rockcrusher trans where ever made. My trans... and car... are dated in the same year and the same month... It's a match! Okay there are NO production numbers present, where they are suppost to be, perhaps this really make this a rare combination!
Last edited by Hammerhead Fred; Sep 3, 2009 at 10:27 AM.
Le Mans Master
Joined: Jan 2006
Posts: 6,504
Likes: 139
From: Butler Pa
You misunderstand the assembly stamp. That transmission was assembled Aug. 28 1970 for the 1971 production model run (see previous post by CCrane72). That fact combined with the missing VIN means it's much more likely that the transmission was an "over the counter" replacement for the original.
How would you ever prove that the missing VIN was a "mistake".My car is a '69 base 300 hp motor. When I bought it, it had a replacement (CE) '70 LT-1 engine, and the correct VIN derivitive is stamped on the original M-21 trans. Just sayin...
