Transmission decoding
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Joined: Oct 2007
Posts: 82
Likes: 7
From: Lakewood Colorado
Transmission decoding
I finally crawled all over my 68 vette to pull up all the numbers. Came to the tranny and I think it's missing the suffix. My tranny code is P8D19__ but as you can see I'm missing the last letter (suffix), A,B of C which tells if it's a M20,M21 of M22. I can't find it anywhere. What I'm I missing? My differential is a AM (3.36). Besides driving it (can't right now because I'm re-wiring the inside) how can I tell what tranny I have?
Melting Slicks
Joined: Aug 2001
Posts: 3,040
Likes: 122
From: Wichita KS
I finally crawled all over my 68 vette to pull up all the numbers. Came to the tranny and I think it's missing the suffix. My tranny code is P8D19__ but as you can see I'm missing the last letter (suffix), A,B of C which tells if it's a M20,M21 of M22. I can't find it anywhere. What I'm I missing? My differential is a AM (3.36). Besides driving it (can't right now because I'm re-wiring the inside) how can I tell what tranny I have?
Melting Slicks
Joined: Aug 2001
Posts: 3,040
Likes: 122
From: Wichita KS
Does the transmission have a drain plug?
All 1963-69 Muncie transmission maincase EXCEPT for the M22, were NOT drilled for a drainplug. The M22 had the front drainplug boss drilled and tapped for a magnetic drainplug. Most original drainplugs are magnetic and have a "P" stamping.
Thread Starter
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Joined: Oct 2007
Posts: 82
Likes: 7
From: Lakewood Colorado
I think i can answer my own question now
Researching more on line it looks as thought the 68 vette did not have a choice in Muncies. I think nly the M20 was offered for 68. Along with that I note a number on the side of my tranny (3925660) which appears to correspond to the M20. Is this right?
Melting Slicks
Joined: Aug 2001
Posts: 3,040
Likes: 122
From: Wichita KS
There may also be some helpful information available from the GM archives at:
http://www.gmheritagecenter.com/gm-h...tion-kits.html
Click on the site. After it loads, scroll down to "Corvette" and click on "show". From the matrix of years, select the year desired (in your case "1968"). Accept the usage agreement. A pdf will download with a lot of useful information about your year car. Save the pdf for later reference.
Transmission information is on pages 27 and 59 of the 1968 pdf.
Hope this helps.
http://www.gmheritagecenter.com/gm-h...tion-kits.html
Click on the site. After it loads, scroll down to "Corvette" and click on "show". From the matrix of years, select the year desired (in your case "1968"). Accept the usage agreement. A pdf will download with a lot of useful information about your year car. Save the pdf for later reference.
Transmission information is on pages 27 and 59 of the 1968 pdf.
Hope this helps.
Melting Slicks
Joined: Aug 2001
Posts: 3,040
Likes: 122
From: Wichita KS
The 3925660 maincase was used on the M20 (wide ratio), M21 (close ratio) and M22 (heavy-duty) transmissions.
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