help with identifying my trans
Thread Starter
Advanced
Joined: Jul 2007
Posts: 99
Likes: 1
From: Iowa Park TX
help with identifying my trans
Have to drop the trans to replace a clutch; what and where am I looking to determine if mine is the M21 or M22 4-speed? Also, which one of the two is called a "rockcrusher" trans? ('70 coupe)
Team Owner
Joined: Jul 1999
Posts: 26,545
Likes: 46
From: Huntersville NC
If your transmission is original, very unlikely to be M22. Only 25 installed in 1970 vettes, we believe they all went into ZR1s, a rare high performance option that looks like the LT1.
There were 4383 M21 "close ratio" transmissions, and by deduction, 7806 M20 "wide ratio" transmissions, the standard 4 spd offered in 1970.
Thread Starter
Advanced
Joined: Jul 2007
Posts: 99
Likes: 1
From: Iowa Park TX
thank you, sir. when I started this project, I threw everything I found (documents wise) into a binder, and I see where you came up with those numbers.
so, how do I tell if it's one of the 4,383 close-ratios, or one of the 7,806 standard 4-speed?
so, how do I tell if it's one of the 4,383 close-ratios, or one of the 7,806 standard 4-speed?
Team Owner
Joined: Feb 2003
Posts: 54,180
Likes: 9,474
From: Sitting in his Nowhere land Hanover Pa
2024 C2 of the Year Finalist - Unmodified
2015 C2 of Year Finalist
depends on if the case as ever been apart or not there was a small metal tag that was bolted to the side of the case. it should have a numbers stamped in them. post them up.
Melting Slicks
Joined: Jun 2006
Posts: 2,071
Likes: 147
From: S Nevada
Here's a pretty good link for the muncie ID. http://www.5speeds.com/muncie2.htm
The M22 really wasn't built for drag racing. It was a road track transmission.
The M22 really wasn't built for drag racing. It was a road track transmission.
Melting Slicks
Joined: Aug 2004
Posts: 2,220
Likes: 6
From: www.Z16.org North/West Pennsylvania
There is a stamp on the passenger side of the transmission. Example P0E03A The last digit, in this example the "A"
Will tell you what it is.
A= wide range M20
B=close range M21
C= Rock crusher M22
Source: 1970-72 NCRS Judging Guide 4th edition.
Will tell you what it is.
A= wide range M20
B=close range M21
C= Rock crusher M22
Source: 1970-72 NCRS Judging Guide 4th edition.
Last edited by garage-ghost; Sep 7, 2011 at 01:29 PM.
