Mark,
In short, yes you will get more top speed at the same RPMs but you will notice that the truck will take a little longer getting up to speed.
I especially like gearing so maybe I can help. A 3.73 rear diff will give the truck plenty of power but the engine will really wind up at highway speeds. It really depends on what kind of driving you plan to do. If you want better highway RPMs (lower RPMs) and better fuel mileage, then you should look for an overdrive transmission with a 0.72 OD gear (0.68-0.78 would be the ideal range). With the OD gear you will not lose any performance in the lower gears at slower speeds and you will enjoy the drop in RPMs at higher speeds.
Many folks decide to swap the rear axle 3.73 gear for a 3.08. That also helps but the down side is a loss of performance in EVERY gear. This is not a problem for a V8 with lots of HP. However, it MIGHT be a problem for a tired inline 6.
If you are opposed to changing transmissions, then the only option is to swap for a taller rear diff gear.
Personally, I like my setup. I have an inline 6 and a 3.73 rear diff matched with a 5 speed transmission with the 0.72 OD gear. I cruise the highway with RPMs around 2100. My MPG is good too.
Last edited by Lugnutz; 11/18/2015 9:47 PM.
