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burnin oil · 10-10-2014, 09:22 AM

Could always pull the diff cover and look and see what the ratio is. The teeth count is stamped into the ring gear. Doing this is the only real way to know what you have. Can also tell real quick if there is a posi unit in there. My 72 K20 has the Eaton rear. As a basic rule of thumb the 3/4 drivetrain is 4.57 gears. 4.10s pretty much only came with the 350 4spd combination. Might be an exception for the Dana axle or it could of been regeared at some point. Gears are readily available for both the Dana 44 and 60. I would keep the heavy drivetrain. I broke more 12bolt rears than I want to think about. Truck 12 bolts are no stronger than a 10 bolt. They are a different animal than car 12 bolts.

10-10-2014, 09:22 AM	#9
burnin oil Registered User Join Date: Jan 2013 Location: Eastern TN Posts: 1,921	Re: 72 K10 SB 1/2 or 3/4 Axles? Could always pull the diff cover and look and see what the ratio is. The teeth count is stamped into the ring gear. Doing this is the only real way to know what you have. Can also tell real quick if there is a posi unit in there. My 72 K20 has the Eaton rear. As a basic rule of thumb the 3/4 drivetrain is 4.57 gears. 4.10s pretty much only came with the 350 4spd combination. Might be an exception for the Dana axle or it could of been regeared at some point. Gears are readily available for both the Dana 44 and 60. I would keep the heavy drivetrain. I broke more 12bolt rears than I want to think about. Truck 12 bolts are no stronger than a 10 bolt. They are a different animal than car 12 bolts.