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Author Topic: 69 Muncie Transmission tag (pn?)  (Read 1796 times)
69Z28-RS
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« on: January 07, 2014, 11:32:21 PM »

The following tag is on the Muncie transmission (M20) in my '69 Z.. which I believe to be totally original.  can someone confirm this is correct for a '69 Muncie M20?  I think the PN reads:   3946797...
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Gary W.  /  69Z28-RS, 72 B 720 cowl console rosewood all tint
69 Corvette convertible, silver/black 350 hp,
60 Corvette white/red, 72 Corvette coupe (2), 
90 ZR1 red/red #246, 90 ZR1 white/gray #2466
72 El Camino, '55 Nomad, '57 Nomad, '57 B/A Sedan
6667ss138
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« Reply #1 on: January 08, 2014, 12:20:45 AM »

Yes, that is the correct M20 tag
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Len H.  Kansas
1969 07A X77D80 Hugger Orange/Black Vinyl Top, complete 3 owner history
1967 Chevelle SS396 138 Convertible/Red/Black int.
1966 Chevelle SS396 138 4sp California/Smog/Black/Red int. POP, original CA black plates
1968RSZ28
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« Reply #2 on: January 08, 2014, 01:36:18 AM »

Gary,

Isn't the partial VIN stamped on the case?

Paul
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69Z28-RS
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« Reply #3 on: January 08, 2014, 12:48:40 PM »

Paul,

Yes, the VIN is stamped along with the application code and the transmission is original, but I didn't know about the tag itself (although most of these were tossed away and back in the '70's when I bought this car, no one would have put one on that didn't belong.  I believe this transmission has never had the side cover off....  car has 75K or so miles (thru 1980..  not driven since).
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Gary W.  /  69Z28-RS, 72 B 720 cowl console rosewood all tint
69 Corvette convertible, silver/black 350 hp,
60 Corvette white/red, 72 Corvette coupe (2), 
90 ZR1 red/red #246, 90 ZR1 white/gray #2466
72 El Camino, '55 Nomad, '57 Nomad, '57 B/A Sedan
bcmiller
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« Reply #4 on: January 22, 2014, 09:43:02 PM »

Gary, what ratio rear axle do you have?  The normal 3.73?  That part number was used for 3.55, 3.73 and I think 4.10 in 1969.
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1968 Camaro SS - now 468 BBC, M21, 12 bolt.
Bryon
69Z28-RS
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« Reply #5 on: January 22, 2014, 09:43:42 PM »

Yes, rear is a BU (3.73:1 ratio)...
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Gary W.  /  69Z28-RS, 72 B 720 cowl console rosewood all tint
69 Corvette convertible, silver/black 350 hp,
60 Corvette white/red, 72 Corvette coupe (2), 
90 ZR1 red/red #246, 90 ZR1 white/gray #2466
72 El Camino, '55 Nomad, '57 Nomad, '57 B/A Sedan
69Z28-RS
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« Reply #6 on: May 08, 2014, 07:53:42 AM »

There's a 'Muncie transmission tag' for sale on ebay
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=161298278028&ssPageName=ADME:B:SS:US:1123

This one is identified as  "1969 Chevelle, Corvette, Camaro Muncie M20 Factory Original Trans Tag 3950356".   This is  different number than on my original M20 Muncie.

Based on bcmiller's post below, were different PN's used on Muncies based on the *rear end ratio*??  Why would they do that??
(I'm trying to learn my 'Camaro new information for the day'...  Smiley
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Gary W.  /  69Z28-RS, 72 B 720 cowl console rosewood all tint
69 Corvette convertible, silver/black 350 hp,
60 Corvette white/red, 72 Corvette coupe (2), 
90 ZR1 red/red #246, 90 ZR1 white/gray #2466
72 El Camino, '55 Nomad, '57 Nomad, '57 B/A Sedan
jdv69z
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« Reply #7 on: May 08, 2014, 08:38:05 AM »

Here's my M20 Tag
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Jimmy V.
jdv69z
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« Reply #8 on: May 08, 2014, 08:41:39 AM »


Based on bcmiller's post below, were different PN's used on Muncies based on the *rear end ratio*??  Why would they do that??
(I'm trying to learn my 'Camaro new information for the day'...  Smiley

Because each different rear end ratio required a different plastic (I think) gear to make the speedometer read correctly.
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Jimmy V.
69Z28-RS
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« Reply #9 on: May 08, 2014, 09:02:19 AM »

Thanks!!   Smiley    That makes sense..    !   Smiley
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Gary W.  /  69Z28-RS, 72 B 720 cowl console rosewood all tint
69 Corvette convertible, silver/black 350 hp,
60 Corvette white/red, 72 Corvette coupe (2), 
90 ZR1 red/red #246, 90 ZR1 white/gray #2466
72 El Camino, '55 Nomad, '57 Nomad, '57 B/A Sedan
JohnZ
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« Reply #10 on: May 08, 2014, 11:36:58 AM »


Based on bcmiller's post below, were different PN's used on Muncies based on the *rear end ratio*??  Why would they do that??
(I'm trying to learn my 'Camaro new information for the day'...  Smiley

Because each different rear end ratio required a different plastic (I think) gear to make the speedometer read correctly.

Actually, the plastic DRIVEN gear was installed at the car assembly plant. What changed was the internal steel DRIVE gear that was pressed on the output shaft at Muncie; there were two different diameter steel DRIVE gears that only worked with two different "families" (diameters) of plastic DRIVEN gears, depending on the axle ratio, and the transmission assembly part number on the steel tag was the only way Muncie or the car assembly plant could tell which transmission they had.
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'69 Z/28
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jdv69z
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« Reply #11 on: May 08, 2014, 01:48:50 PM »

So there were 2 diff parts no.s for each of the 3 trans - M20, M21, and M22?
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Jimmy V.
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« Reply #12 on: May 08, 2014, 02:17:32 PM »

All covered in the AIM- M20-A1 I had asked about this sometime back about the difference in the part numbers for different RPO's. M20 was either 3950356 or 3946797 for 1969 depending on RPO and Gear ratio. Might as well put other #'s while I am looking at page-M21= 3950316 or 3946798, M22-3950318
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Putting you First...Keeps me First. Talent on loan from God. Helping the hobbyist and exposing the fraud
1969 SS/RS 396 coupe Hugger Orange X22 712 bought in 79
1969 SS 350 coupe LeMans Blue 713 bought in 79
1969 307 4spd. coupe Daytona Yellow 711 bought in 85
69Z28-RS
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« Reply #13 on: May 08, 2014, 02:19:51 PM »


Based on bcmiller's post below, were different PN's used on Muncies based on the *rear end ratio*??  Why would they do that??
(I'm trying to learn my 'Camaro new information for the day'...  Smiley

Because each different rear end ratio required a different plastic (I think) gear to make the speedometer read correctly.

Actually, the plastic DRIVEN gear was installed at the car assembly plant. What changed was the internal steel DRIVE gear that was pressed on the output shaft at Muncie; there were two different diameter steel DRIVE gears that only worked with two different "families" (diameters) of plastic DRIVEN gears, depending on the axle ratio, and the transmission assembly part number on the steel tag was the only way Muncie or the car assembly plant could tell which transmission they had.

Thanks JohnZ... Smiley    you came thru with factual 'new information' for the day ..  AGAIN..  Smiley

*(and Bentley).*  You posted while I was typing.. Smiley
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Gary W.  /  69Z28-RS, 72 B 720 cowl console rosewood all tint
69 Corvette convertible, silver/black 350 hp,
60 Corvette white/red, 72 Corvette coupe (2), 
90 ZR1 red/red #246, 90 ZR1 white/gray #2466
72 El Camino, '55 Nomad, '57 Nomad, '57 B/A Sedan
jdv69z
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« Reply #14 on: May 08, 2014, 02:53:47 PM »

So I'm assuming the M22 was only available over a narrow range of rear end ratios, thus only needing 1 part no.?
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Jimmy V.
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