Changing from 3.73 to 4.10 gears

Turtle n Peeps wrote:

parker.rowe wrote:

Huntindog wrote:
Ford 2015 towing guideShows that a 4.30 truck can tow 3000# more than a 3.73 truck.

Yeeeep. Guess the people who designed the truck say they make a difference.

Yes, that's because a short gear will give you a better duty cycle. That's why a 450, 550 with the same engine tranny combo will give you a more choices of shorter gears.

Here is a great article that tells you about the myth of torque vs HP. Read the article and then read #1. The guy is spot on if you do the math.

I have an issue with the last part of this statement.

Enough theory: Lets see an understandable example of torque and horsepower

Let’s say that you are loading the back of your pickup with rocks. The bed is two feet high, and you lift six fifty-pound rocks in one minute. You have done 2 feet x 300 lbs = 600 ft-lbs of work. Power is determined by how fast you do this work, so you have done 600 ft-lb of work in 60 seconds, requiring 600 ft-lbs / 60 seconds = 10 ft-lbs/sec of power. A horsepower is 550 ft-lbs/sec, so you have used 10 / 550, or .018 horsepower. So, now let’s say that you work twice as fast, and lift 12 rocks in a minute in place of the 6. You have now loaded your pickup using .036 horsepower. Note that in both cases, you have exerted the same force (torque) when lifting each rock of 2 ft x 50 lbs = 100 ft-lbs. In the second case, however, it required twice as much power with the same amount of torque.
This is because the torque was occurring at a higher rate of speed.


So it isn't the same amount of torque, 12 rocks at 50 lbs ea is 600#, 2' X 600 lbs = 1,200ft-lbs of work.

So 1,200 ft-lbs / 60 sec = 20 ft-lbs per sec of work, or .036 Hp

In the second case you did twice the work in the same time, requiring twice the HP.

This is great in Theory and math formula.

It doesn't seem to workout in real life, most HD Pickups gas engines High HP/Low Torque ratio top out at about 16,000# towing capacity with most needing 4.30 to 4.60 gears to get there at near 4,500 to 5,000 rpm.

Today's Diesels with low hp/Torque ratio are rated to to tow nearly twice that amount about 30,000 lbs with 4.10 gears and maybe 3,000 rpm.

I my personal case my 2001 Cummins factory rated at 235 HP and 410 ft-lbs of torque, is likely near 300 HP and 610 ft-lbs of torque. I have added a DS Power Puck (50 HP and 140 ft-lbs claimed increase) and a set of RV275 injectors. The math is 275 + 50 = 325, but in reality not likely cumulative increase so about 300 HP. Torque 410 + 140 = 550, have never seen a torque rating for RV275 injectors so 60 ft=-lbs is a guess. My TV has 3.55 gears currently the GCVW of my rig is 20,500 lbs, I can put that up a 7 percent grade at 55 mph in direct drive (4th gear) at about 2,500 RPM.

So while love Theory and Math, when it comes to the power difference between a gas engine and a diesel it doesn't always seem to work out.