Rear end housings different for 3 series vs 4 series carriers? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Gibson · 01-31-2019, 03:26 PM

I'm pretty sure I have 3.08s in the 12 bolt on my 78 C10 currently. I'm planning to moving to 3.73.

Were the housings different between those that came with 3 series carriers vs 4 series carriers?

I ask because my plan was to get a posi (open currently) and change the gears at the same time. I just don't want to find out too late it won't fit in the housing.

This is probably a stupid question, but I haven't been able to find anything definitive one way or the other.

**mongocanfly** · 01-31-2019, 03:29 PM

Way back yonder in them old days I went from 2.73s to 5.13s...same axle..different carrier..

Gibson · 01-31-2019, 03:44 PM

Thanks Mongo - that seemed like it would work, but when I asked the company I'm planning on getting the new posi (True-Trac) and ring from, they said I would need a thicker gear. That didn't make sense to me because the TrueTrac takes a 3.73 and up, which would make it a 4 series. So if I got a new ring and pinion, and I swapped the carrier over to the TrueTrac it seems like that would make everything fall where it needs to.

It made me suspicious that something was different on the axle itself as far as spacing.

01-31-2019, 03:26 PM	#1
Gibson Registered User Join Date: Jul 2009 Location: Maryville, TN Posts: 132	Rear end housings different for 3 series vs 4 series carriers? I'm pretty sure I have 3.08s in the 12 bolt on my 78 C10 currently. I'm planning to moving to 3.73. Were the housings different between those that came with 3 series carriers vs 4 series carriers? I ask because my plan was to get a posi (open currently) and change the gears at the same time. I just don't want to find out too late it won't fit in the housing. This is probably a stupid question, but I haven't been able to find anything definitive one way or the other.

01-31-2019, 03:29 PM	#2
mongocanfly Post Whore Join Date: May 2015 Location: Alabama Posts: 14,674	Re: Rear end housings different for 3 series vs 4 series carriers? Way back yonder in them old days I went from 2.73s to 5.13s...same axle..different carrier.. __________________ Mongo...aka Greg RIP Dad RIP Jesse 1981 C30 LQ9 NV4500..http://67-72chevytrucks.com/vboard/s...d.php?t=753598 Mongos AD- LS3 TR6060...http://67-72chevytrucks.com/vboard/s...34#post8522334 Columbus..the 1957 IH 4x4...http://67-72chevytrucks.com/vboard/s...63#post8082563 2023 Chevy Z71..daily driver

01-31-2019, 03:44 PM	#3
Gibson Registered User Join Date: Jul 2009 Location: Maryville, TN Posts: 132	Re: Rear end housings different for 3 series vs 4 series carriers? Thanks Mongo - that seemed like it would work, but when I asked the company I'm planning on getting the new posi (True-Trac) and ring from, they said I would need a thicker gear. That didn't make sense to me because the TrueTrac takes a 3.73 and up, which would make it a 4 series. So if I got a new ring and pinion, and I swapped the carrier over to the TrueTrac it seems like that would make everything fall where it needs to. It made me suspicious that something was different on the axle itself as far as spacing.



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