Posted by Matt Wilson on Tuesday, December 28, 2004 at 11:03AM :
In Reply to: Re: How much can I upgrade my 48B1.. posted by Rick on Monday, December 27, 2004 at 2:20PM :
I seriously doubt that the engine would have enough power to take advantage of the higher gearing that you would get from having overdrive and 4.89 axle gears. The drag of the air flowing over the vehicle (or rather that vehicle pushing through the air) increases as a square function of the road speed. Meaning that a jump in road speed from, say, 60 mph to 70 mph, would result in a 36% increase in drag, which has to be overcome by the engine. So even though the gearing would theoretically allow the truck to travel that fast, it's doubtful that the engine would be able to produce enough torque to overcome drag and get you to that speed. With just 4.89's, I find that I don't have much extra power when travelling at 55 mph. There is a little, and I have gotten to, or close to 60, but I don't think I could get any faster. Maybe if you added all of the performance goodies to the engine, you might be able to go faster, but that seems like it would be awfully hard on the engine to push it that much for sustained periods of time.
By the way, I think I forgot to mention in my other posts that 4.89's were a factory option, so I don't think you'd be reducing the value of your truck by installing them. However, if I had the money to do it over again, I would seriously consider installing and overdrive, but leaving the 5.83's in place. You get the best of both worlds that way - acceptable highway performance, but also great low gearing for off-road use. But then again, that's not original, but it is easy enough to remove the OD if desired.