Rear end swap '90 12 bolt into '71 - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**LEEVON** · 07-09-2008, 12:49 AM

My cousin has a low mile 12 bolt posi 3.73 rear end from a '90 454SS truck for sale and I'm thinking of replacing my factory open diff 3.73 rear. Does anybody know if the width is compatible with the factory '71 1/2 ton 5-lug? If it is the same or very close, would I just be looking at adding the coil spring perches / removing leaf perches?

Thanks in advance!

Blazer1970 · 07-09-2008, 06:52 AM

I am not sure about the width (I think they are a lot wider), but that axle will be a corp. 9 1/2" often referred to as the "semi-floating 14 bolt".

07-09-2008, 12:49 AM	#1
LEEVON Registered User Join Date: Jul 2006 Location: Ozark, MO Posts: 4,887	Rear end swap '90 12 bolt into '71 My cousin has a low mile 12 bolt posi 3.73 rear end from a '90 454SS truck for sale and I'm thinking of replacing my factory open diff 3.73 rear. Does anybody know if the width is compatible with the factory '71 1/2 ton 5-lug? If it is the same or very close, would I just be looking at adding the coil spring perches / removing leaf perches? Thanks in advance! __________________ '20 Silverado Trail Boss ~ '17 Tahoe ~ '79 K15 Sierra Grande ~ '76 Blazer 2wd ~ '71 Cheyenne swb ~ '55 Pontiac Safari ~'50 3100 bagged ~ '80 Wife ~ Late model kids

07-09-2008, 06:52 AM	#2
Blazer1970 Registered User Join Date: Dec 1999 Location: Old Mission, MI, USA Posts: 2,510	Re: Rear end swap '90 12 bolt into '71 I am not sure about the width (I think they are a lot wider), but that axle will be a corp. 9 1/2" often referred to as the "semi-floating 14 bolt". __________________ Tim



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