The 1947 - Present Chevrolet & GMC Truck Message Board Network - View Single Post - 47-59 Transmission Swap

weim55 · 05-13-2020, 10:57 PM

I did this exact swap once on a 50 3100 1/2 ton. The SM 420 was out of a ‘51 with a torque tube extension housing. Other than switching out the floor plate for the taller four-speed transmission it was a direct bolt in. I changed absolutely nothing else, The original driveshaft and Torque tube worked just fine. If my memory serves me I do believe the yolk and U joint Assembly coming off the back of the SM 420 are unique to the transmission. My ‘51 replacement transmission came with that so it wasn’t an issue but keep that in mind if you’re buying a used unit. Maybe someone on here can chime in about that to confirm.

Steve weim55 Colorado

05-13-2020, 10:57 PM	#7
weim55 Registered User Join Date: Jan 2017 Location: Larkspur, Colorado Posts: 916	Re: Transmission Swap I did this exact swap once on a 50 3100 1/2 ton. The SM 420 was out of a ‘51 with a torque tube extension housing. Other than switching out the floor plate for the taller four-speed transmission it was a direct bolt in. I changed absolutely nothing else, The original driveshaft and Torque tube worked just fine. If my memory serves me I do believe the yolk and U joint Assembly coming off the back of the SM 420 are unique to the transmission. My ‘51 replacement transmission came with that so it wasn’t an issue but keep that in mind if you’re buying a used unit. Maybe someone on here can chime in about that to confirm. Steve weim55 Colorado Last edited by weim55; 05-13-2020 at 11:02 PM.