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| | | | Joined: Oct 2004 Posts: 348 Shop Shark | | Shop Shark Joined: Oct 2004 Posts: 348 | were Gmc trucks ever 12 volt positive ground? | | | | | Joined: May 2006 Posts: 8,351 'Bolter | | 'Bolter Joined: May 2006 Posts: 8,351 |
Bill Burmeister
| | | | | Joined: Feb 2006 Posts: 1,867 Shop Shark | | Shop Shark Joined: Feb 2006 Posts: 1,867 | Okay to add to the question what about some of the goofier 12 and 24 volt BIG trucks and military models? I thought GMCs were all positive ground until 1956ish when 12 volt was standardized? | | | | | Joined: May 2006 Posts: 8,351 'Bolter | | 'Bolter Joined: May 2006 Posts: 8,351 | I don't really know about military trucks or the big trucks, but when the light trucks went to 12 volt ('55 2nd for GMC and Chevy), they went to negative ground, too.
Bill Burmeister
| | | | | Joined: Sep 2007 Posts: 154 Wrench Fetcher | | Wrench Fetcher Joined: Sep 2007 Posts: 154 | All systems with six volt are positive ground. When the change from six to twelve was made then also the switch was made to negative ground. There may be some military vehicle or the like which may be the exception to the rule.
Way back when ?? the thought was that positive ground six volt systems had better cranking power for starting. | | | | | Joined: May 2001 Posts: 7,438 Extreme Gabster | | Extreme Gabster Joined: May 2001 Posts: 7,438 | All systems with six volt are positive ground. This is true with GMCs but not with most other brands. | | | | | Joined: Feb 2006 Posts: 1,867 Shop Shark | | Shop Shark Joined: Feb 2006 Posts: 1,867 | I still thought GMC did 6 volts up until 1956, and Chevy did it until 1955. Anyone have any info on that? | | | | | Joined: Sep 2001 Posts: 29,269 Bubba - Curmudgeon | | Bubba - Curmudgeon Joined: Sep 2001 Posts: 29,269 | Yes, you are correct for GMC. I think it is also possible for GMC trucks to have 6v positive and/or 12v negative as factory options up to 1957 (and maybe 1958). There's GMC literature at this website that describes 6v and 12v standard and optional equipment for different sized GMC trucks. Tim | | | | | Joined: May 2006 Posts: 8,351 'Bolter | | 'Bolter Joined: May 2006 Posts: 8,351 | Very interesting. Looks like the models that had the 6 volt option were carryover bodies from the '54 model year.
Bill Burmeister
| | | | | Joined: Sep 2001 Posts: 29,269 Bubba - Curmudgeon | | Bubba - Curmudgeon Joined: Sep 2001 Posts: 29,269 | Yes, and in 1956, GMC had a factory option 12v to 6v converter to provide power to older 6v trailers. | | | | | Joined: Feb 2006 Posts: 1,867 Shop Shark | | Shop Shark Joined: Feb 2006 Posts: 1,867 | Tim thanks for the cool source of info! | | |
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