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| | | | Joined: Oct 2008 Posts: 321 'Bolter | | 'Bolter Joined: Oct 2008 Posts: 321 | Okay, I'm working on my '63 C20 LWB stepside, and I'm keeping her stock. So, that means keeping the granny 4 spd and 5.56 rear gears. That's right, 5.56:1. She was built for pulling. Like I tell everyone, with the 292, 4 spd, and 5.56 rear, she will pull a house off it's foundation.....slowly  So, the big question is how fast will she go on the highway. I'm thinking I will be very lucky to hit 55, but what do you guys think?
1963 Chevy C20 Longbed Stepside
1978 Chevy K30 Custom Deluxe
| | | | | Joined: Sep 2009 Posts: 21 New Guy | | New Guy Joined: Sep 2009 Posts: 21 | I think you are about right, maybe 5 one way or the other, | | | | | Joined: May 2010 Posts: 47 Wrench Fetcher | | Wrench Fetcher Joined: May 2010 Posts: 47 | Not very.  | | | | | Joined: Jul 2008 Posts: 1,262 Shop Shark | | Shop Shark Joined: Jul 2008 Posts: 1,262 | (revised for 5.14 gear) Assuming a 28 inch dia. tire... 4000 RPM 64.82 MPH 3500 RPM 56.72 MPH 3000 RPM 48.62 MPH 2500 RPM 40.52 MPH 2000 RPM 32.41 MPH Assuming a 30 inch dia. tire... 4000 RPM 69.46 MPH 3500 RPM 60.77 MPH 3000 RPM 52.09 MPH 2500 RPM 43.41 MPH 2000 RPM 34.73 MPH Assuming a 33 inch dia. tire... 4000 RPM 76.40 MPH 3500 RPM 66.85 MPH 3000 RPM 57.30 MPH 2500 RPM 47.75 MPH 2000 RPM 38.20 MPH Bigger diameter rear tires = faster highway speed at given rpm Bigger diameter rear tires = more clutch slipage to get the truck moving. Not a problem though with your "granny tranny". ( I am running 33" dia. tires on my truck) Above data calculated using this website: http://www.wallaceracing.com/gear-speed.phpHope that helps!  John
Last edited by Hot Rod John; 07/04/2011 3:01 PM.
| | | | | Joined: Sep 2006 Posts: 841 Shop Shark | | Shop Shark Joined: Sep 2006 Posts: 841 | i have the same gearing. i cruze at 3000 rpms at about 52 to 54mph. noone else likes it at the speeds they drive and i get a lot of "one finger salutes". both are just a sign of the times i guess. | | | | | Joined: Nov 2006 Posts: 231 'Bolter | | 'Bolter Joined: Nov 2006 Posts: 231 | I ain't in no rush either!
1963 Chevy C-10 Fleetside 1970 C-30 Dump Truck 2025 Silverado High Country 2500 Diesel 2012 Indian Chief Vintage serial #002 motorcycle 1946 Indian Chief, 1947 Indian Chief w/sidecar,2014 Indian Chieftain, 2015 Indian Scout | | | | | Joined: Nov 2004 Posts: 1,552 Shop Shark | | Shop Shark Joined: Nov 2004 Posts: 1,552 | | | | | | Joined: Oct 2008 Posts: 321 'Bolter | | 'Bolter Joined: Oct 2008 Posts: 321 | Thanks for all the responses, I figured the ol girl would be puttering down the road. Tony, it's got 5.56 rear gears. The rear end it has in it was an option and also has a dealer installed No-Spin locker. That is one of the reasons I am keeping this truck stock.
1963 Chevy C20 Longbed Stepside
1978 Chevy K30 Custom Deluxe
| | | | | Joined: May 2006 Posts: 8,351 'Bolter | | 'Bolter Joined: May 2006 Posts: 8,351 | It should be a 4.56 or a 5.14, those were the only options. The 4.56 is a more common of the two, as it was the standard gear for the 3/4 ton.
Bill Burmeister
| | | | | Joined: Oct 2008 Posts: 321 'Bolter | | 'Bolter Joined: Oct 2008 Posts: 321 | I had to do some looking.... Yes, it has the 5.14's. Not sure why I had 5.56 in my head. I looked up all the info in my books to verify.
1963 Chevy C20 Longbed Stepside
1978 Chevy K30 Custom Deluxe
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