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camrycurt · 09-17-2010, 08:19 AM

I'm a complete noobie here as well so take this with a grain of salt, but my understanding is that the SM420 heavy duty transmission that GM used through the mid-60s had that shift pattern, with R up and over to the top left and then the standard H for 1-4. You say yours is geared pretty low - could it maybe be the 420 with granny low?

Does it have a high hump with the shifter coming right out of the top? If yes, then maybe you've got a 420 in there?

Hope that helps.

09-17-2010, 08:19 AM	#7
camrycurt Registered User Join Date: Jul 2010 Location: Leesburg, VA Posts: 420	Re: Transmission shift pattern? I'm a complete noobie here as well so take this with a grain of salt, but my understanding is that the SM420 heavy duty transmission that GM used through the mid-60s had that shift pattern, with R up and over to the top left and then the standard H for 1-4. You say yours is geared pretty low - could it maybe be the 420 with granny low? Does it have a high hump with the shifter coming right out of the top? If yes, then maybe you've got a 420 in there? Hope that helps.