Is this worth keeping? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

MAK191 · 11-17-2009, 08:39 AM

So I have a 72 Chevy C10 with a 307/th350 that I have bee working on for the last couple months, and lurking on the boards. I also acquired a 70 GMC 250 with 3 speed manual parts truck in the process that I got for cheap. Now my question is about the rear end from the GMC. It is a posi and my Chevy is not. I really don't have the money to pay someone to swap over the differentials so I can use it on my 72, but is it going to be something I regret later if I get rid of it? Is the stock posi from 70 a good one or a bad one? I really could use the money for other parts, but I don't want to do something stupid. I also know that i could re-drill the lug pattern, but isn't the 70 axle shorter and won't it have gears that are too low? What do you guys think?

-Mike

PanelDeland · 11-17-2009, 09:27 AM

Factory gearing is
Auto -3:08
3 Speed-3:73
Unless optioned otherwise.Also you probably have a coil set-up on the Chevy and leafs on the GMC.If they are both leafs or both coils you could swap the complete rearend.
3:73's would be quite low for street use with the auto.Widths may also be different.IIRC the change came in late 70 so depending on when the rear was built it could be the same,again IIRC.

MAK191 · 11-17-2009, 09:54 AM

Thanks for the reply. Sorry I forgot to metion that they both have coil springs.

11-17-2009, 08:39 AM	#1
MAK191 Registered User Join Date: Nov 2009 Location: FL Posts: 335	Is this worth keeping? So I have a 72 Chevy C10 with a 307/th350 that I have bee working on for the last couple months, and lurking on the boards. I also acquired a 70 GMC 250 with 3 speed manual parts truck in the process that I got for cheap. Now my question is about the rear end from the GMC. It is a posi and my Chevy is not. I really don't have the money to pay someone to swap over the differentials so I can use it on my 72, but is it going to be something I regret later if I get rid of it? Is the stock posi from 70 a good one or a bad one? I really could use the money for other parts, but I don't want to do something stupid. I also know that i could re-drill the lug pattern, but isn't the 70 axle shorter and won't it have gears that are too low? What do you guys think? -Mike

11-17-2009, 09:27 AM	#2
PanelDeland I am a Referee of life. Join Date: Jun 2000 Location: Greensboro N.C. Posts: 13,992	Re: Is this worth keeping? Factory gearing is Auto -3:08 3 Speed-3:73 Unless optioned otherwise.Also you probably have a coil set-up on the Chevy and leafs on the GMC.If they are both leafs or both coils you could swap the complete rearend. 3:73's would be quite low for street use with the auto.Widths may also be different.IIRC the change came in late 70 so depending on when the rear was built it could be the same,again IIRC. __________________ The 47-present Chevrolet and GMC Truck Message Board Network,it's owners,moderators,members,and associates of any type should not be held responsible for my opinion. You can't fix stupid,not even with duct tape. "My appearance is due to the fact that "GOD" does punish you for having too much fun!" Barrett-Jackson has perfected alchemy,they make rust into gold! "You can lead a horse to water but you can't saddle a duck" "Cleverly disguised as a 'Responsible Adult' "Sometimes your Knight in shining armor is just a retard in tinfoil"

11-17-2009, 09:54 AM	#3
MAK191 Registered User Join Date: Nov 2009 Location: FL Posts: 335	Re: Is this worth keeping? Thanks for the reply. Sorry I forgot to metion that they both have coil springs.

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