Needed M20 4 speed truck trany - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**burb71** · 09-09-2004, 07:37 PM

Are all 67-72 M20 tranys the same? Meaning, does it matter the size of the engine it's mated to 6 cyl - V8?
I have a 72, 402 and want a truck M20 behind it. If anyone has one please respond with a price.
I am confused because GM used one option code for the 4 speed trany in our trucks (M20).

1969 GMC · 09-09-2004, 09:55 PM

Gm's designation of the truck 4 speed as M20 is confusing to say the least. However, there are 2 different trannies it could be. The SM420 was offered from about 1947 til 1967, it is a slightly more compact and lightweight transmission, but very durable. Parts may be hard to find.
The 2nd is the SM465, introduced in 1968. It is bigger and heavier than the SM420, and was used until at least 1991.
It did not matter what size engine for the 4 speed to be optioned, the only diff is that 67 is the last year for SM420.

*botboy* · 09-09-2004, 11:27 PM

I have an SM420 2WD for sale, $105 but its a bit far from you...

**burb71** · 09-10-2004, 04:12 AM

Thanks for the helpful Imfo "1969 GMC"

MOTHERTRUCKERS · 09-10-2004, 06:03 AM

Rebuilt sm465 last year 200.00, can be worked off with labor LOL.

09-09-2004, 07:37 PM	#1
burb71 Active Member Join Date: Oct 2002 Location: Ft. Myers, Fl Posts: 1,716	Needed M20 4 speed truck trany Are all 67-72 M20 tranys the same? Meaning, does it matter the size of the engine it's mated to 6 cyl - V8? I have a 72, 402 and want a truck M20 behind it. If anyone has one please respond with a price. I am confused because GM used one option code for the 4 speed trany in our trucks (M20).

09-09-2004, 09:55 PM	#2
1969 GMC Registered User Join Date: Feb 2003 Location: The Rubber City Posts: 5,498	Gm's designation of the truck 4 speed as M20 is confusing to say the least. However, there are 2 different trannies it could be. The SM420 was offered from about 1947 til 1967, it is a slightly more compact and lightweight transmission, but very durable. Parts may be hard to find. The 2nd is the SM465, introduced in 1968. It is bigger and heavier than the SM420, and was used until at least 1991. It did not matter what size engine for the 4 speed to be optioned, the only diff is that 67 is the last year for SM420. __________________ 1969 GMC K2500 1996 Honda Accord 2007 Kawasaki KLR 650

09-10-2004, 06:03 AM	#5
MOTHERTRUCKERS Registered User Join Date: Dec 1999 Location: BRADENTON FLA Posts: 3,269	Rebuilt sm465 last year 200.00, can be worked off with labor LOL. __________________ Rest in Peace Ed. Thanks for all the good times.

09-09-2004, 11:27 PM	#3
botboy Account Suspended Join Date: Dec 2003 Location: Delano, MN Posts: 630	I have an SM420 2WD for sale, $105 but its a bit far from you...

09-10-2004, 04:12 AM	#4
burb71 Active Member Join Date: Oct 2002 Location: Ft. Myers, Fl Posts: 1,716	Thanks for the helpful Imfo "1969 GMC"



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