Need help decoding transmission (68 427 4-speed)
Thread Starter
Instructor
Joined: Aug 2008
Posts: 115
Likes: 4
From: Denison Texas
Need help decoding transmission (68 427 4-speed)
Ok, I read several other threads concerning this topic and found a lot of conflicting information and would like some clarity from those that have been in my shoes.
I have a 68 427/390 (4-speed) I know that it is VERY unlikely that this is an M22, but I thought I'd amuse myself since I finally have her up on a lift.
looking for information on my Muncie 4-Speed and here are the numbers:
3925660 passenger side casting number
P8T26 passenger side casting number
186408799 (matches my VIN) passenger side STAMP - Vertical
-------------------------
-------------------------
3915088 (Metal data tag bolted to bottom of drivers side plate)
3884685 Drivers side Casting
If I have to remove the plate and inspect the angle of the gears, I will....that time is coming anyway.
Thanks for any info in the decode...
Mike
I have a 68 427/390 (4-speed) I know that it is VERY unlikely that this is an M22, but I thought I'd amuse myself since I finally have her up on a lift.
looking for information on my Muncie 4-Speed and here are the numbers:
3925660 passenger side casting number
P8T26 passenger side casting number
186408799 (matches my VIN) passenger side STAMP - Vertical
-------------------------
-------------------------
3915088 (Metal data tag bolted to bottom of drivers side plate)
3884685 Drivers side Casting
If I have to remove the plate and inspect the angle of the gears, I will....that time is coming anyway.
Thanks for any info in the decode...
Mike
Account disabled by user request 5 Jan 09
Joined: Jan 2005
Posts: 261
Likes: 1
I have a 68 427/390 (4-speed) I know that it is VERY unlikely that this is an M22, but I thought I'd amuse myself since I finally have her up on a lift.
3925660 passenger side casting number
P8T26 passenger side casting number
186408799 (matches my VIN) passenger side STAMP - Vertical
3915088 (Metal data tag bolted to bottom of drivers side plate)
3884685 Drivers side Casting
Mike
3925660 passenger side casting number
P8T26 passenger side casting number
186408799 (matches my VIN) passenger side STAMP - Vertical
3915088 (Metal data tag bolted to bottom of drivers side plate)
3884685 Drivers side Casting
Mike
P8T26 decodes to Muncie 4-speed, December 26, 1967.
3925660 and 3884685 are casting numbers for M20, M21 and M22.
3915088 tag decodes to M20 (see AIM, page M20, A1).
M22 would have factory lower drain plug, M20 and M21 not. But, many owners have drilled their own lower plug, so that's not definitive.
------------------------------------
PS ... the transmission is 18S (not 186)
Last edited by FrankVincent; Sep 11, 2008 at 10:31 PM.
Melting Slicks
Joined: Mar 2005
Posts: 2,187
Likes: 7
From: Chetwynd B.C.
serial number 08799 is early January 1968 build.
P8T26 decodes to Muncie 4-speed, December 26, 1967.
3925660 and 3884685 are casting numbers for M20, M21 and M22.
3915088 tag decodes to M20 (see AIM, page M20, A1).
M22 would have factory lower drain plug, M20 and M21 not. But, many owners have drilled their own lower plug, so that's not definitive.
------------------------------------
PS ... the transmission is 18S (not 186)
P8T26 decodes to Muncie 4-speed, December 26, 1967.
3925660 and 3884685 are casting numbers for M20, M21 and M22.
3915088 tag decodes to M20 (see AIM, page M20, A1).
M22 would have factory lower drain plug, M20 and M21 not. But, many owners have drilled their own lower plug, so that's not definitive.
------------------------------------
PS ... the transmission is 18S (not 186)
Thanx FrankVincent, that helped me too.
Now I know for sure that I have an M21 in my '68. I checked the AIM, page M20, A1 and it shows my 3915090 is an M21 with my L79. 
I owe you a (I have the AIM book but didn't know where to exactly look)Being an M21 will it be the Close Ratio? or Wide ratio? I assume it will be the Close.
shmoky
Last edited by shmoky; Sep 12, 2008 at 06:59 PM. Reason: added question
