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Mod | | | Forums66 Topics128,192 Posts1,057,353 Members48,469 | | Most Online14,466
Apr 26th, 2026 | | AD Chevy Trucks  Over 6,000 pictures Brad Allen has an awesome collection of Chevrolet factory pictures that he has set up from film strips. Check them out!
Lots of work on Brad's part ... pure enjoyment (and references) for you!
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| | | | Joined: Jan 2010 Posts: 41 New Guy | | New Guy Joined: Jan 2010 Posts: 41 | my 62 is running 3.73 in the rear end and hit freeway speed alright, but is humming pretty good...
anyone gone from 3.73 to 3.55? is there much of a difference? | | | | | Joined: Nov 2002 Posts: 1,002 Shop Shark | | Shop Shark Joined: Nov 2002 Posts: 1,002 | There are RPM calculators on the web that will tell you what your rpm is for a given rear axle ratio and tire size. Here's one there are others; http://www.csgnetwork.com/multirpmcalc.htmlI went from 4.56 to 3.73 in my 68 C20 with 327. I wanted to be under 2500 rpm at 65 mph, and 3.73 doesn't do it. A 3.55 would just get me there, 3.30 would be better. My tire size is 265/75 16. Hope that helps. Larry
I don't own a vehicle that isn't old enough to drink.
| | | | | Joined: Feb 2006 Posts: 564 Shop Shark | | Shop Shark Joined: Feb 2006 Posts: 564 | I went from 3.73 to 3.42 in the Dana 44. I'm very happy with it.
I've also got a 4spd manual OD trans, and it skips down the highway at 80mph effortlessly.
-Brad
SOUTHERN FALL GABfestOctober 6 ~ Commerce, Georgia Details here!Never Pee on an Electric Fence. | | | | | Joined: Sep 2009 Posts: 21 New Guy | | New Guy Joined: Sep 2009 Posts: 21 | I have a 64 3/4 ton GMC pu , I went from 4.10 to 3.53 gears and droped from about 3300 rpm's to about 2600-2700 rpm's at about 65-70mph. the truck has a dana 60 with 235-85-16 tires.Hope this helps mikie | | |
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