Gas, Diesel, Gears and Towing
Help me to understand the differences. Why can three trucks that are identical other than engines and transmissions (understanding that a diesel truck will have a higher GVWR and a lower payload becau...
Forum Discussion
BIG ISSUE! not being mentioned.
GCWR is a performance rating.
IE how fast it will go at gcw, with X s ft of frontal area, at a given aerodynamic flow, on a given Y% grade, on a given temperature day. The JSAE specs have this minimum as 35 mph, or 40 mph depending upon the gvwr of the truck. IIRC this is an over or under 15K lbs. So if said truck is a 550, and it goes 37 mph.....meets spec. Same with a 15-45 rig, if it goes 40+ mph, it meets spec. This may NOT be your spec! If you have a trailer that that gives you a total of 100 sq ft, spec is max 80 sq ft, you may very well find yourself going slower that that 35/40 mph. OR, you may find yourself going faster, it that given trailers aerodynamics are better overall than the base version tested. One may overheat, the other may not! You may find this speed to be too low! so it does not meet YOUR spec, but meets these engineers that feel this is a minimum spec!
Another spec. minimum gradability this is 12% IIRC.
If you are like me, you drive on roads and grades that are in the 20-30% range, you may very well stall your rig out, and not go up said hill! Been there did that done that, to the tune of a $3000 auto trans that was geared too tall in first gear! I can name many roads here in the seattle area that are at or above 15-18%, including multiple driveways of decent size that a minimum spec rig will not go up! There is a formula that can tell you how steep a grade you can pull, based on tire diam, axel ratio, 1st gear in trans, and torque of the motor. HP means nothing at these slow speeds! On a freeway grade, HP is the better number to use, again, there is a formula that will tell you about how fast you can go on a freeway grade too.....
BIG trucks, ie class 6 and above, the sales reps have the ability to drivetrain spec a rig to be either a freeway rig, or more of a local off road rig. My Navistar for example, is more of a local rig. WIth a 175/335 non turbo V8, it moves 26K on local roads, on a freeway, I'm missing some 50+ HP. BUT, do to its really low 10.08 first gear, 4.33 axle gears, same diam tires as my old 05 dmax dually, it can pull 30K up a 30% grade. Granted a freeway grade of 2-4%, I'm doing 30-40mph. My dmax on the other hand, can only do a 25% grade, at 20K lbs! But same load on a freeway grade, I'm doing 50+ mph! Depending upon what roads are in front of me, tells me which rig I want to do the towing with. As one will get close really fast, but not make it to the end, if there is a steep grade. The other, will get to the end, but do it in what should be a slower overall time, assuming both get to the end.
Also, a rule of thumb I learned back in the 70s, max trailer behind a truck is 2x GRAWR. While you can go a bit higher, this is where the tail can wag the dog issue, push the TV down a steeper hill etc ratio. Can you do more, oh sure. I have found thru the years this ratio to be a good one for how much I want to keep max weight wise on ANY of the trucks I've owned, from a 76 Toyota, to the largest the Navistar dump flatbed.
Staying under the given ratings. NOT ALWAYS hunky dory! If you load a trailer incorrectly, while you have rating to work with, if the tail is too heavy, you have no hitch wt, trailer fishtail sways by itself.....you are not safe, yeah under ratings. But you are an accident waiting to happen!
Many things to keep in mind when it comes to what is the best, worst, or what will be ok towing.
I'' also take my 96 K3500 CC as my best overall family towing. I was typically towing some 2000-3000 lbs over the gcwr. BUT< compared to the auto rig with a 14500 gcwr. My 5 sp 6.5td pulled, did not overheat etc compared to my rig with a 12500 gcwr. It could out pull at low speeds my dmax too, a bit over 30% at 20K lbs. Again slower on the freeway! Put 80K miles with my family of 6 in that truck at 15-16K lbs total. Up to local ski areas in the winter, yes I towed an rv trailer in the snow, chained up multiple times. A few longer trips in the summer, a few weekends in summer, more in winter skiing....
Choose your rig wisely! Do not always trust the numbers!
Marty
GCWR is a performance rating.
IE how fast it will go at gcw, with X s ft of frontal area, at a given aerodynamic flow, on a given Y% grade, on a given temperature day. The JSAE specs have this minimum as 35 mph, or 40 mph depending upon the gvwr of the truck. IIRC this is an over or under 15K lbs. So if said truck is a 550, and it goes 37 mph.....meets spec. Same with a 15-45 rig, if it goes 40+ mph, it meets spec. This may NOT be your spec! If you have a trailer that that gives you a total of 100 sq ft, spec is max 80 sq ft, you may very well find yourself going slower that that 35/40 mph. OR, you may find yourself going faster, it that given trailers aerodynamics are better overall than the base version tested. One may overheat, the other may not! You may find this speed to be too low! so it does not meet YOUR spec, but meets these engineers that feel this is a minimum spec!
Another spec. minimum gradability this is 12% IIRC.
If you are like me, you drive on roads and grades that are in the 20-30% range, you may very well stall your rig out, and not go up said hill! Been there did that done that, to the tune of a $3000 auto trans that was geared too tall in first gear! I can name many roads here in the seattle area that are at or above 15-18%, including multiple driveways of decent size that a minimum spec rig will not go up! There is a formula that can tell you how steep a grade you can pull, based on tire diam, axel ratio, 1st gear in trans, and torque of the motor. HP means nothing at these slow speeds! On a freeway grade, HP is the better number to use, again, there is a formula that will tell you about how fast you can go on a freeway grade too.....
BIG trucks, ie class 6 and above, the sales reps have the ability to drivetrain spec a rig to be either a freeway rig, or more of a local off road rig. My Navistar for example, is more of a local rig. WIth a 175/335 non turbo V8, it moves 26K on local roads, on a freeway, I'm missing some 50+ HP. BUT, do to its really low 10.08 first gear, 4.33 axle gears, same diam tires as my old 05 dmax dually, it can pull 30K up a 30% grade. Granted a freeway grade of 2-4%, I'm doing 30-40mph. My dmax on the other hand, can only do a 25% grade, at 20K lbs! But same load on a freeway grade, I'm doing 50+ mph! Depending upon what roads are in front of me, tells me which rig I want to do the towing with. As one will get close really fast, but not make it to the end, if there is a steep grade. The other, will get to the end, but do it in what should be a slower overall time, assuming both get to the end.
Also, a rule of thumb I learned back in the 70s, max trailer behind a truck is 2x GRAWR. While you can go a bit higher, this is where the tail can wag the dog issue, push the TV down a steeper hill etc ratio. Can you do more, oh sure. I have found thru the years this ratio to be a good one for how much I want to keep max weight wise on ANY of the trucks I've owned, from a 76 Toyota, to the largest the Navistar dump flatbed.
Staying under the given ratings. NOT ALWAYS hunky dory! If you load a trailer incorrectly, while you have rating to work with, if the tail is too heavy, you have no hitch wt, trailer fishtail sways by itself.....you are not safe, yeah under ratings. But you are an accident waiting to happen!
Many things to keep in mind when it comes to what is the best, worst, or what will be ok towing.
I'' also take my 96 K3500 CC as my best overall family towing. I was typically towing some 2000-3000 lbs over the gcwr. BUT< compared to the auto rig with a 14500 gcwr. My 5 sp 6.5td pulled, did not overheat etc compared to my rig with a 12500 gcwr. It could out pull at low speeds my dmax too, a bit over 30% at 20K lbs. Again slower on the freeway! Put 80K miles with my family of 6 in that truck at 15-16K lbs total. Up to local ski areas in the winter, yes I towed an rv trailer in the snow, chained up multiple times. A few longer trips in the summer, a few weekends in summer, more in winter skiing....
Choose your rig wisely! Do not always trust the numbers!
Marty
