O.k. I have this 12 bolt truck axle in my '55 GMC. Will any GM posi fit this axle. The axle is a '73-'87 type. It is a 6 bolt (wheel). I plan on changing out the axle to a 5 hole GM so I have a better choice of wheels. I saw a 12 bolt posi unit for sale. The seller called it a 3 series? What will fit? Thanks in advance. Kent
probably a question for the guys over on the Chevy truck board. http://67-72chevytrucks.com/ There are a number of us from here on the HAMB over there too. The six lug rear end you have now should be a 4x4 rear end if it is from the mid 70's. I think you can just swap axles and drums if you just want to change to 5 lug for a wheel change. I'm not positive on what he is calling a 3 series rear end but am pretty sure he is saying that it has 3 something gears in it and has the carrier for those gears while a 4.11 and up rear end has a different carrier. I slid over an checked. Scroll down to the 7th post in this thread, he explains it pretty well. http://www.67-72chevytrucks.com/vboard/showthread.php?t=235117
3 series 12 bolt truck carrier is for 3.42 and down gears.4 series is 3.73 and up. 12 bolt truck and car have a different pinion gear diameter,I think the ring gear is the same.The truck and car 12 bolt carriers are not supposed to interchange so make sure of what you are buying.Generally you can swap 12 bolt truck 5 lug axles for 6 lug axles if the spline count and length is the same.
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