rear axle gear ratio

Y'all have too much time on your hands! Lol
Can't we just get back to "my truck will whoop your truck's arse"?

I just watched the 2016 Duramax pull 21400 up the Ike.

Doing the same math the Duramax lifted 30,000 lbs the 2225 ft in 9 minutes 48 seconds....so 206 HP. It averaged 49 mpg so that would have taken about 80 HP. So it put out 286 HP and the rated Hp is 397. I never noticed in the video where the Duramax shifts at but I think it revs higher than the Powerstroke and Cummins. It might have averaged 370 crankshaft HP. 286/370 gives it a 77% rating on the Super Ike Dynometer.

Edit:
I screwed up. It would likely take more like 70 rear axle Hp to overcome rolling resistance and drag on the GMC and its trailer at 49 mph. So 276/370 = 75% efficiency. So all three work out very close to the same thing. The Ford should have been forced to shift into 3rd gear at 2400 rpm and it would have made much better use of its power. As for the trucks ability to put their engine's power to the ground goes it looks as though all three are very comparable.

Cummins12V98 wrote:
4x4ord

My 11 HO Dually dynode 304 out of 350 that's 87 percent. The newer RAM's are at that percent of higher. The Ford's are less than 80 as you noted.

Let's compare the results of the Ike dyno run

The Ram lifted 38600 lbs 2225 ft in 12 minutes 28 seconds. That required 2225 x 38600/748/550 or 209 HP. (1 hp is the power required to lift 550 lbs 1 ft in 1 second)
Additionally the Cummins provided power to overcome rolling resistace and drag. It pulled the 8 mile hill at an average speed of 38.5 mph. This would have required approx 62 Hp. If the Hp of the Cummins is 352 @ 2100 and 385 at 2800 then a the engine would have averaged somewhere close to 369 HP throughout the run. So 271/369 gives the Ram a 73% efficiency rating on the Super Ike dyno.

So now the Ford:
38600 x 2225/683 seconds / 550 ft lbs/sec = 229 HP. Additionally the Powerstroke provided the power to run the race at an average speed of 42 mph....about 69 Hp. The Ford ran between 2100 and 2800 rpm where it produces between 366 and 440 HP. So the average crankshaft output of the Powestroke should have been somewhere close to 403 HP. And (229+69)/403=74%.

4x4ord

My 11 HO Dually dynode 304 out of 350 that's 87 percent. The newer RAM's are at that percent of higher. The Ford's are less than 80 as you noted.

BenK wrote:
Sign of the times...semantics or the evolution/slang usage in our language...

Just like when pointed out the difference between the original usage
vs todays usage of 'motor' vs 'engine'

Am going to start referring to an ICE's starter as a 'starter engine'...doesn't
sound right does it?...well at least to my earballs... :B

Lost to too many is that HP is derived from torque...if there is
no torque...there can be *NO* horsepower...

Or that there can be 1,000,000 ft/lbs of torque, but no HP...yet... :?

So, torque is power, HP is power...POWER is torque or HP in today's usage... :S

Turtle n Peeps wrote:
Ben, even these guys are screwed up.

Hotrod wrote:
Similarly, if the gear ratio is 3.08:1, then the output torque will be 308 lb-ft. It’s easy to see that the lower 4.10:1 gears put more power to the ground than the higher 3.08:1 gears. Keep in mind that the engine’s power has not changed but that the available torque to the tires has.

Even the writer of this article is trying to use torque and power interchangeably which you can't do. Then at the last he gets is straight and correct.

It's no wonder people are confused. :R

I am having trouble understanding your argument. It sounds like you are saying that people don't understand what they are talking about when they use terms like torque and power therefore the true meaning of torque and power is lost

It's kind of like because people say "I could care less what you think" instead of properly saying "I couldn't care less what you think" we should understand what the person means and instead of correcting the error make both phrases mean the same thing

Sign of the times...semantics or the evolution/slang usage in our language...

Just like when pointed out the difference between the original usage
vs todays usage of 'motor' vs 'engine'

Am going to start referring to an ICE's starter as a 'starter engine'...doesn't
sound right does it?...well at least to my earballs... :B

Lost to too many is that HP is derived from torque...if there is
no torque...there can be *NO* horsepower...

Or that there can be 1,000,000 ft/lbs of torque, but no HP...yet... :?

So, torque is power, HP is power...POWER is torque or HP in today's usage... :S

Turtle n Peeps wrote:
Ben, even these guys are screwed up.

Hotrod wrote:
Similarly, if the gear ratio is 3.08:1, then the output torque will be 308 lb-ft. It’s easy to see that the lower 4.10:1 gears put more power to the ground than the higher 3.08:1 gears. Keep in mind that the engine’s power has not changed but that the available torque to the tires has.

Even the writer of this article is trying to use torque and power interchangeably which you can't do. Then at the last he gets is straight and correct.

It's no wonder people are confused. :R

Cummins12V98 wrote:
"Edit: @2100 rpm the new Cummins is likely able to produce close to 360 Hp so it would still be pulling very well down to 2100 rpm/53 mph in 4th gear."

My 33K combined load seems to end up there on a lot of 6 percent grades.

Something doesn't add up. A 33k truck and trailer sitting on a 6% grade in park will have a torque of exactly 2635 lbft on the axle to hold the truck from rolling down the hill. Now if your engine is going to maintain that torque and turn the axle the 472 rpm required to move you're truck 45 mph it will need to deliver 472 x 2635 x pi/16500 or 237 Hp to the rear axle to overcome the force produced by you truck and trailer on a 6% grade.


In order for your truck to be moving at a constant 45 mph down the highway it also requires a certain amount of torque and rpm (power). Assuming your truck gets 10 mpg, it is burning 1/10 of a gallon per mile or 4.5 gallons per hour at 45 mph. 1 gallon of diesel contains about 55 hp hours. Your engine is not running real efficient cruising down the highway so say it is turning 33% of that diesel fuel to rear axle HP. So .33 x 4.5 x 55 = 82 Hp. So your engine needs to provide 82 rear wheel HP to overcome rolling resistance and drag at 45 mph.

So 237 + 82 = 319 rear axle Hp are required to move a 33k truck and trailer up a 6% grade at 45 mph. In all this calculating the assumptions made are the 33% efficiency of your engine and the 10 mpg fuel economy. Both these assumptions are going to be reasonably close.

Now, it seems as though rear wheel Hp is often about 78% of crankshaft power so 319 rear wheel Hp would be equivalent to 410 crankshaft HP. I going to guess your truck would be able to hold 42 mph pulling a 6% grade.

"Edit: @2100 rpm the new Cummins is likely able to produce close to 360 Hp so it would still be pulling very well down to 2100 rpm/53 mph in 4th gear."

My 33K combined load seems to end up there on a lot of 6 percent grades.

I think many people are confused about torque, power, and gear ratios and with the new transmissions it probably isn't really that big of deal anymore. I liked the way Ford engineers used to make the gear ratio choice for their customers. If you wanted a SRW you had a choice between 3.31 or 3.55 but if you got 20" rims the 3.31 was not available. Choose a one ton dually and you got 3.73 gears. If you were planning on pulling heavier yet you were encouraged to purchase an F450 and you got 4.30 gears.

GM was out pulling everyone and they made it real simple....you want a Duramax - you get 3.73 gears.

Ben, even these guys are screwed up.

Hotrod wrote:
Similarly, if the gear ratio is 3.08:1, then the output torque will be 308 lb-ft. It’s easy to see that the lower 4.10:1 gears put more power to the ground than the higher 3.08:1 gears. Keep in mind that the engine’s power has not changed but that the available torque to the tires has.

Even the writer of this article is trying to use torque and power interchangeably which you can't do. Then at the last he gets is straight and correct.

It's no wonder people are confused. :R