Gas engine and Diesel of same specs.Pull the same.

JustLabs wrote:

jerem0621 wrote:
People just think that a diesel working hard at 2500 rpm's is ok and that 4500 in a gasser is NOT ok.

Thats exactly right. There were numerous times I had my '07 5.9 CTD running at 2900 rpm while pulling a long steep grade.

Let me tell you,listening to a CTD at those RPM gets old in a hurry.

I would have much rather listened to my '01 8.1 liter big block spin along at 4500 pulling those same grades.

Mine pulling a combined load of 28,000# up the Grapevine at 2,900 rpm in 3rd gear sounds very nice!

They should handle the load about the same in the same truck. The only difference is the weight of the truck. A heaver TV handles a trailer better. Also a longer truck handles a trailer better. But just between engines, you will be happier with the diesel. Company I used to work for had a 05 Dually 6.0 Gas job, and a 06 Dually with a LBZ. Pulling the same trailers with the same weight on them, the 6.0 was lucky to see 5 mpgs, while the LBZ saw 12-13. Plus with the LBZ, you would forget its back there. They both pulled the same from what I heard. Never drove the gas job, the engine blew up at around 125K miles, while the Duramax had twice that and is still running strong. They were usually around 35K GCVW all day. I am reminded everyday why I bought a Duramax, the 6.0 Chevy I have at work feels like its trying to pull the moon with just a little single axle 3K pump behind it.

I will never go back to a gas truck or one with out training wheels

Hi ramyankee -

2006 5.9 Cummins with 147,000 miles, 6spd trans, don't remember rear ratio - on the weekend I hauled a 39ft x 13ft high tri axle toyhauler 100 miles round trip, GC wt 24,000lb. 24 miles in 30 mph crosswind, 38 miles 30 mph headwind, 38 miles 30 mph tailwind. Rolling country with 3 or 4 hills about a mile long guessing 6% to 8%. I had to shift to 5 to hold 55 mph on the steepest hill, against the wind. The rest of the trip was on cruise, 65mph/2100 rpm in the big sprocket. Trip meter registered 12 mi/US gal for the round trip.

Not sure how an 8.1 gas would compare in the same conditions.

Horsepower is horsepower. Two prime movers with the same HP will pull the same load up the same hill at the same speed. I don't care if it's gasoline, diesel, electricity, or steam powering them. Just let them operate at the speed they develope that power and ignore the sound they make.

Gasoline does loose some to diesel in thet more gear reduction can mean more parasitic losses and less HP delivered to the ground. The turbocharger also gives the diesel an advantage at higher elevations. the playing field may level if turbocharging becomes popular on larger displacement gasoline engines. A 5.0L ecoboost would be a good 3/4 and 1-ton truck engine for part time towing IMHO.

Sometimes the gasoline engine will win simply because the diesel can't spin fast enough to make the speed while delivering its extra torque to the ground.

Diesel will almost always win the fuel efficiency award. Whether or not it saves enough fuel to pay for itself has to be determined on a case by case basis.

ramyankee wrote:
By my sig, i pull with a 2002 8.1.....Its specs are roughly 340HP and 455 lb ft of torque. If a guy were to opt for a 2000-2002 Cummins, approx the same specs, does a Diesel pull any easier. Just a thought.
I realize they tow at a much lower RPM.
Thanks. Just curious.

I would include the '03/'04 HPCR 305/555 HO Cummins in your looking. Cummins made it just those two years. Its a lot quieter and has much more towing power than the '00-'02 models that put out 235/460 for the auto and 245/505 for the NV5600 tranny. You also get the much improved 48RE auto tranny with the HO.

I had a '01 2500 Dodge/Cummins 235/460 47RE tranny 3.54 that was noisey enough to kill normal brain cells. Plus the 3.54 gears with the 47RE was rated at 9800 lbs tow capacity. It was a sick puppy in OD but ran good in drive

I have a '03 305/555 HO with the NV5600 3.73 axle. I pull a my 11200 lb 5er and a 10k bumper pull and a 14k GN flatdeck and a 16k 36' triaxle GN stock trailer.

The stock trailer is joint owned with a neighbor who pulls it with a '04 2500 chevy 8.1/Allison. At a full 16k load on the triaxle trailer he can out accelerate me for the first couple of blocks but after that the Cummins slowly leaves him behind.

I've had the Cummins way up in the 2600-2700 rpm range a couple of times but all it did was make more racket. I keep the rpms in the 2200-2400 range pulling the 16k triaxle up any grades at legal speeds or my 11200 lb 5er up mountain passes like Monarch or Parleys canyon I-80 east out of Salt Lake or Eisenhower tunnel grade in the 2300-2400 rpm range at normal speeds.

ib516 wrote:
The diesel will pull at lower rpm with much less transmission shifting. It will also get 50% better mpg towing or empty.

Lower rpm = lower road speed, unless you run in a higher gear which means lower torque at the wheel. You can't have it all unless you've got HP. I seriously doubt a stock 235hp diesel with similar torque to a 345hp gas engine would pull as well but I can't say I've had first hand experience. Modded is another story for either engine.

The 2001 & 2002 5.9L Cummins was 235hp/460tq (auto or 5 speed) or 245hp/505tq H.O. (6speed stick only) from the factory.

The diesel will pull at lower rpm with much less transmission shifting. It will also get 50% better mpg towing or empty.

However, if you were to add a set of six Rv275 injectors ($300 and ~40hp) and a $100 Edge EZ box good for another 50hp or so at the rear wheels, and that 02 Cummins would leave the 8.1L sucking its tailpipe.

That's how I had my 2002 2500 modded. It was absolutely amazing towing or empty. Sadly, the old quad cab (half sized back doors) was just too small for my growing family.

340 ft/lbs vs 800 ft/lbs. Yes there is a Santa Claus, Virginia.

If the diesel's operating range is from 1400 rpm to 2900 and the gasoline engine might be expected to operate from 1400 to say 4200 rpm. At 1400 rpm the gasoline engine won't make much power but it needs to run slow if its going to get descent fuel economy when cruising empty. For this reason you might want both the gas and diesel to have similar gears for cruising empty down the highway. When pulling a heavy trailer up a hill the diesel will be happy at say 1800 to 2900 rpm where as the 8.1 liter gas engine is going to need 3500 rpm before it starts making some ponies. So now if the gasoline engine is going to be expected to pull like the diesel in low gear its going to need a 7.25 ratio rear end to compete with the diesels 3.73 ratio.

camping man wrote:
I had a 92 Volvo semi tractor with 300hp Cummins, lets see a 300hp pickup truck out pull that up a grade at 80k, must be all perception.

ALL other things being equal, YES it would. That semi probably had 900 plus lb/ft tq and 16 gears?