โOct-01-2018 08:57 AM
โOct-04-2018 10:14 PM
โOct-04-2018 08:12 PM
4x4ord wrote:
To pull your 20500 lb unit up a 7% grade at a steady 55 mph would require very close to 290 rear wheel horsepower. (Exactly 210 HP to raise the load up the elevation gain plus another roughly 80 HP to overcome wind and rolling resistance) That means something like 342 engine horsepower. So long as the vehicle is geared appropriately it makes no difference whether that 342 HP is being generated by a diesel engine running at 2500 rpm, a gasoline engine running 4500 rpm or an electric motor running 1750.
Edit: I corrected a calculation error but even if your truck is capable of putting 85% of its engine's power to the pavement it would only be capable of 50 mph pulling 20500 lb gcvw up a 7% grade... and this assumes only 65 hp is being used to overcome wind and rolling resistance. I'm thinking the hill you've measured your speed on is not marked accurately or is not a constant 7% grade.
โOct-04-2018 07:30 PM
โOct-03-2018 01:18 PM
rhagfo wrote: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
Letโs 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 letโs 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.
โOct-03-2018 09:36 AM
Huntindog wrote:
Torque matters.
All of the Diesel guys are debating when the TQ numbers will go over 1000, and which brand will do it first...
Let me show in simple math why the engine race isn't all it's cracked up to be.
Lets say your motor has 500 TQ.
And your 1st gear is 6 to 1.
You will have 3,000 TQ!, leaving the tranny.
If your differential ratio is 3 to 1, you will have 9,000 TQ!, to the rear wheels.
If the diff is 4 to 1, it will be 12,000 torque!!
These are BIG numbers, so big that it makes the manufacturers adding 20-50 #s to the motors, seem like small potatos.... Of course an extra 50 TQ would mean an extra 900-1,200 to the rear wheels.
That is the secret magic of gearing.
โOct-02-2018 09:35 PM
dodge guy wrote:
With a 3500lb CCC he will be hard pressed to get anywhere near that 14k lb rating!
โOct-02-2018 06:44 PM
โOct-02-2018 01:36 PM
โOct-02-2018 01:33 PM
oakmandan wrote:Considering it is not used for general commuting and you have the top two gears locked out.... I would go 4.56/4.88 and start using those top two gears. 4.30 minimum if spending money. If you get off pavement much also consider a pair of TrueTrac differentials at the same time.
Thanks for the input. I have mastered the 6 speed and lock out 6th and 5th most of the time. The truck is not an everyday driver. It is the 5th wheel puller and Mama's grocery getter. I am no where near my GVWR. We watch closely how we load it.
โOct-02-2018 11:58 AM
quora.com wrote:
Click For Full-Size Image.
Assume the smaller gear is driven by a motor producing X units of power. This energy is used to rotate smaller gear. To turn the gear faster you'll need more power. Smaller gear in turn rotates the bigger (driven) gear.
If smaller gear rotates 4 times per second, bigger gear will rotate only once per second. {because, smaller gear (9 teeth) has to rotate 4 times to traverse all the 36 teeth of bigger gear.}
Now,
Power is constant (since energy is conserved)**
Bigger gear rotates 4 times slower than smaller gear {i.e. Angular speed is 1/4th the smaller gear}
We can easily see,
Power = Constant
Angular Speed1 = 4*Angular Speed2
Torque1*Angular Speed1 = Torque2*Angular Speed2
Hence, Torque2 = 4*Torque1 {i.e. Bigger gear produces 4 times bigger torque. Torque is multiplied.}
If you get an opportunity to observe gearbox of an automobile, do observe the sizes of 1st, 2nd and 3rd stage gears. You'll observe the 1st is the biggest gear and then size reduces successively. This is because initially car needs maximum torque and bigger gear would result is larger torque multiplication
โOct-02-2018 11:20 AM
โOct-02-2018 10:46 AM
enblethen wrote:
specs for 320MKS show GVW as 13,995. That is real close to 14,000
โOct-02-2018 09:01 AM
โOct-02-2018 08:25 AM
Bud
USAF Retired
Pace Arrow
โOct-02-2018 07:00 AM
Crabbypatty wrote:
I just looked up your fiver and its max is 14,000# thats places you 2000# over the limit of what you can tow. Find a scale and see what you weigh as you might be overloaded for the truck set up.