I would think a 3.07 would be considered a highway gear. I drove a F@^& F250 daily for 5 years with a 4 speed NP435 and a 4.10 rear end. Yes it was churning 4000 rpm at 80 mph, but I drove it from OKC to dallas and back that way many times. Of course it only got 7 mpg but I never had any major problems. On the other hand, my 2006 Silverado with the 5.3 liter engine has a 3.23 rear end and will barely get out of it's own way from a stop. It runs under 2000 rpms at 70 in overdrive. If I had an older truck with a 1:1 direct drive top gear, I'd want a 3.43-3.73 ratio for good acceleration and highway speed. As far as the 4 speed goes, I'd keep it and change the rear axle (I'm a truck driver so I appreciate that extra low gear!)
Last edited by Chris_Welch; 01/10/2011 11:45 PM.
