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- - Changing gear ratio question (https://67-72chevytrucks.com/vboard/showthread.php?t=688772)

wcstory

11-16-2015 04:15 PM

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

LVPhotos

11-16-2015 04:23 PM

Re: Changing gear ratio question

http://cdn1.bigcommerce.com/server70...g?t=1398725710

LostMy65

11-16-2015 04:31 PM

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.

wcstory

11-16-2015 08:37 PM

Re: Changing gear ratio question

Well crap 4.10 doesn't get me there!

TJ's Chevy

11-16-2015 09:32 PM

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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