1970 3/4 Ton Posi Swap - The 1947 - Present Chevrolet & GMC Truck Message Board Network

70C20TPI · 10-24-2003, 10:03 PM

Does anybody know which years of rear differentials are interchangeable with a 70 3/4 ton 2wd? I want to swap my non-posi corporate 10-bolt out for a posi unit. The only local differential with posi that I can find is a 10 bolt from a 66 3/4 ton. Both vehicles have coil springs. Would it be intechangeable? Alternatively, does anybody have a posi differential for sale in or close to Utah that would swap in without modifications?

Rod · 10-25-2003, 09:43 AM

It's an easy swap if it's a corporate, pull the whole third member and put it in.... you dont even have to lift the truck off the ground. I have a corporate posi for sale if needed. You can just put a detroit locker unit in also. Private message me if you like, or email me. 66 will probably have some really steep 4.57 ratio gears. If you have a dana rear diff then you have to be fairly handy at meshing gear patterns and backlash setting, best left to a shop. Rod

10-24-2003, 10:03 PM	#1
70C20TPI Registered User Join Date: Oct 2003 Posts: 1	1970 3/4 Ton Posi Swap Does anybody know which years of rear differentials are interchangeable with a 70 3/4 ton 2wd? I want to swap my non-posi corporate 10-bolt out for a posi unit. The only local differential with posi that I can find is a 10 bolt from a 66 3/4 ton. Both vehicles have coil springs. Would it be intechangeable? Alternatively, does anybody have a posi differential for sale in or close to Utah that would swap in without modifications?

10-25-2003, 09:43 AM	#2
Rod Join Date: Dec 1999 Location: Eastern - Manitoba Canada, Winnipeg Posts: 4,369	It's an easy swap if it's a corporate, pull the whole third member and put it in.... you dont even have to lift the truck off the ground. I have a corporate posi for sale if needed. You can just put a detroit locker unit in also. Private message me if you like, or email me. 66 will probably have some really steep 4.57 ratio gears. If you have a dana rear diff then you have to be fairly handy at meshing gear patterns and backlash setting, best left to a shop. Rod __________________ Senior active founding member. 70 3/4 ton GMC Suburban 4x4 250/4 spd. 71 1/2 ton Suburban Chevy 4x4, 350/350 72 Chev 1 ton tow truck 402BB w/Holmes 440 wrecker on propane 2005 FLSTSCI Harley Springer 85 FXSB Harley Lowrider 72 Triumph 650 Bonneville 5spd "Poor people don't have hobbies" Quote from wife.



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