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11-16-2015, 04:15 PM
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#1 |
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Registered User
 
Join Date: Jun 2006
Location: Cape Cod, Ma.
Posts: 236
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Changing gear ratio question
Currently my 1966 GMC 2500 has 4.56 gears behind a SM420 four speed trans. I top out at 45-50 mph.
II wanted to find a 3.73 full floater, but came across a full floating rear with 4.10 gears. Will this be enough a ratio drop to get me to 60-65 mph
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1966 GMC 1 Ton 305 V6 SM420 4 speed - retired Fire Dept Support Truck from Little Falls, NJ My GMC Photos Last edited by wcstory; 11-16-2015 at 04:26 PM. |
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11-16-2015, 04:23 PM
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#2 |
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Registered User
Join Date: Jan 2013
Location: Las Vegas, NV
Posts: 1,857
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Re: Changing gear ratio question
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1962 shortbed 408cui small block, TKO 600 5-speed, bagged Porterbuilt suspension. 18" Salt Flats http://www.cardomain.com/ride/332579...t-c-k-pick-up/ http://67-72chevytrucks.com/vboard/s...d.php?t=560081 |
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11-16-2015, 04:31 PM
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#3 |
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But Found Her 25yrs Later!
Join Date: Oct 2010
Location: Oregon City, Oregon
Posts: 10,527
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Re: Changing gear ratio question
There's a few rpm calculators out there, but I've always preferred the one LVPhotos shared because it's all there in one chart.
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I lost my 65 - Found it 25 years later: http://67-72chevytrucks.com/vboard/s...d.php?t=426650 66 C20 Service Truck: http://67-72chevytrucks.com/vboard/s...d.php?t=428035 |
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11-16-2015, 08:37 PM
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#4 |
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Registered User
Join Date: Jun 2006
Location: Cape Cod, Ma.
Posts: 236
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Re: Changing gear ratio question
Well crap 4.10 doesn't get me there!
__________________
1966 GMC 1 Ton 305 V6 SM420 4 speed - retired Fire Dept Support Truck from Little Falls, NJ My GMC Photos |
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11-16-2015, 09:32 PM
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#5 |
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Registered User
Join Date: Mar 2013
Location: Southern Oregon
Posts: 10,384
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Re: Changing gear ratio question
3.73 at 65 was 2800 for me with 30 inch tires with a 4 speed.
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1966 Chevy C10 "Project Two Tone" http://67-72chevytrucks.com/vboard/s...d.php?t=596643 1964 GMC "Crustine" semi-build:http://67-72chevytrucks.com/vboard/s...d.php?t=665056 My youtube channel. Username "Military Chevy": https://www.youtube.com/channel/UC_h...fzpcUXyK_5-uiw |
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