What rear end gears do I have, or how do I find out? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

BIG CTY · 11-06-2006, 08:54 PM

I'm thinking 3:73' s because thats what I read in some book. But my indy said that she has 4:11's in her. He has a 65 C10. So which one is it?

62 short step · 11-06-2006, 09:31 PM

Some times the factory will stamp the ring & pinion gear teeth on the cover. But your best bet is to pop the cover off count the teeth and divide them.

60-66 Nut · 11-07-2006, 10:57 AM

Like 62 short step said, the most accurate way is to pull the cover and count the ring and pinion teeth. There should be some numbers stamped on the axle tube that indicate the original ratio, but in 40 years anything could have been changed. If you don't want to pull the cover, you can always check it by marking it. Just jack up one rear wheel, mark the tire and the driveshaft, then turn the wheel two full revolutions while counting the driveshaft revolutions. Three driveshaft revolutions = 3.00:1, three and a half = 3.50:1, etc. If your truck has a positrac rearend, you'll probably have to jack up both rear wheels and turn them one full revolution. 3.73's were the most common ratio on these old trucks, but 3.07 and 4.11 were an option. Best of luck.

60-66 Nut

11-06-2006, 08:54 PM	#1
BIG CTY Between the earth and the sky Join Date: Oct 2006 Location: Chesapeake, VA Posts: 822	What rear end gears do I have, or how do I find out? I'm thinking 3:73' s because thats what I read in some book. But my indy said that she has 4:11's in her. He has a 65 C10. So which one is it? __________________ Chris - 1966 C10 Shortbed Fleetside, 1991 GMC Sierra 1500 Extended Cab, 1993 Blazer Sport 4x4 My other rides: 1969 Chevrolet Impala SS427 Convertible 1976 Dodge Tradesman B200 2002 Nissan Maxima 6 speed 2004 Mercedes Benz CL500

11-06-2006, 09:31 PM	#2
62 short step Senior Member Join Date: Aug 2005 Location: Greenwell Springs, Louisiana Posts: 2,882	Re: What rear end gears do I have, or how do I find out? Some times the factory will stamp the ring & pinion gear teeth on the cover. But your best bet is to pop the cover off count the teeth and divide them. __________________ www.louisianaclassictruckclub.com 1965 c-10 86 chevy c/k 20

11-07-2006, 10:57 AM	#3
60-66 Nut Professional Beer Tester Join Date: Aug 2004 Location: Louisiana Posts: 453	Re: What rear end gears do I have, or how do I find out? Like 62 short step said, the most accurate way is to pull the cover and count the ring and pinion teeth. There should be some numbers stamped on the axle tube that indicate the original ratio, but in 40 years anything could have been changed. If you don't want to pull the cover, you can always check it by marking it. Just jack up one rear wheel, mark the tire and the driveshaft, then turn the wheel two full revolutions while counting the driveshaft revolutions. Three driveshaft revolutions = 3.00:1, three and a half = 3.50:1, etc. If your truck has a positrac rearend, you'll probably have to jack up both rear wheels and turn them one full revolution. 3.73's were the most common ratio on these old trucks, but 3.07 and 4.11 were an option. Best of luck. 60-66 Nut __________________ 60 Ford F100 Custom Cab 61 Apache Short Fleetside 64 C10 Short Stepside 65 C80 409 V8 5spd(X-Firetruck) 83 GMC 350 Olds Diesel 85 GMC Short Bed 86 GMC Short Bed 90 GMC R3500 Crew Cab 92 GMC 1500



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