Tell me about these tranny numbers (4 speed)
10-30-2006, 05:58 PM
#1
Safety Car
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Location: VASS, NC, USA
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Tell me about these tranny numbers (4 speed)
Tranny removed out of my 68 bb roadster. Id appreciate if someone could decipher these tranny numbers so Im absolutely sure what to order for a rebuild (M-21 or 22)
Inspection/shift lever cover: 3884685
There is an inspection tag: 3 (or 8, hard to tell as the first number is partially covered by the a bolt) 915091
Case number: 3925660
Tailshaft housing: 385758
date code: P8A18
VIN numbers match my 68 BB roadster
Inspection/shift lever cover: 3884685
There is an inspection tag: 3 (or 8, hard to tell as the first number is partially covered by the a bolt) 915091
Case number: 3925660
Tailshaft housing: 385758
date code: P8A18
VIN numbers match my 68 BB roadster
10-31-2006, 01:03 PM
#2
Team Owner
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Location: Washington Michigan
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Casting numbers check out, and the Muncie date code is January 18, 1968. If the input shaft is the original, an M20 will have two grooves in the splines, M21 has one, and M22 has none; many replacement input shafts had no grooves for I.D. at all. 1968 M22's had a drain plug, although some rebuilders add them routinely, as the boss for the plug is in all main cases. Highly unlikely that it's an M22, as only 80 were sold in '68, and they were all attached to L-88's. 
11-02-2006, 09:24 AM
#3
Melting Slicks
A transmission that sounds like a blower drive when driving is an M-22. There are many swap meet M-22's identified by the drain plug that are simply 3925661 main case castings that were in use from 1970 thru 74. All of these castings had drain plugs regardless if they were M20, M21 or M22. People love to say they have a Rockcrusher. Very few drivers want to hear it.
11-05-2006, 09:47 AM
#5
Melting Slicks
And your site is the definitive site. You taught me!
12-06-2006, 10:35 PM
#6
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A really informative paper, thanks. I've got an M22 sitting in a garage corner after replacing it with an M20, which is more practical for a street car. But I sure love the M22 howl, and am saving this trans for a future hot rod project.
