Hey guys, need some clarification on some stuff. I'm on another forum and a guy I know claims his truck will out tow a gasser just because it's a diesel. Before I indulge, let me say I pretty much zero experience towing, so everything I know is in theory.




That said, this is the story. He has a 1991 Dodge with a 5.9L Cummins turbo diesel he says is rated 160hp and 400 lb-ft of torque @ 1,600 (I know this much is true), that he says can pretty much out tow any gasser. I invited him to trying towing with the beloved 460. He later claimed he has all sorts of towing experience (thousands and thousands of miles of many combinations: exact words) and nothing touches a Cummins. Typical fanboy right?

So as you know I reminded him about the 460, which in it's best year produced 245 horsepower and 385 lb-ft of torque. The torque comes in a bit higher in the RPMs as well all know however. I also am aware he'd get the better fuel efficiency.

He wanted to continue arguing.

I brought up gearing. Now, I know technically using a t-case for towing isn't good for it in 4WD, so lets pretend it's a center differential with the 4LOW ratio of a BW 1356 which is 2.69 IIRC. With An NP435, 2.69 T-Case/CD and either 4.56 or 5.13 gears, it would have a total crawl gear roughly 4 times lower than the diesel truck. With similar torque specs and nearly 100 horsepower more, shouldn't the 460 eat it in ability since the Dodge has no center differential and is directly tied to the axle from the transmission (and no granny gear might I add)?

 

For any imaginary truck you can build around a 460 I'm sure your friend can build another around a Cummins. I imagine whichever of you has the best imagination will be able to out-tow the other.

 

Ok so lets remove the variables. Same power output at the same RPM, wouldn't the lowered geared truck be able to tow more/better?

 

Only one way to find out
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Who did, exactly?

I don't know anybody who tows a camper at rock crawling speeds.

Manufacturers match an axle ratio to the output of the engine they're installing. That's why you see 300-6s with 3.08s and 302s with 3.55s and lower. So the 460 has lower gears because it needs it. The 5.9L has higher gears because it has the power to back it up. (6.7L Powerstrokes have 3.31s ) The 5.9L, stock for stock (which is the only practical way to make a comparison), will walk away from the 460 any day. So what's your point? You've lost and you came here for a bailout LOL

 

Theres a YouTube video out there where a vw toureg drags a Cummins & a durochoke.

 

Not really, I just wanted some clarification. I figured when equal figures go in together the lower gear will come out on top. I still don't really see your point. The 460 should come out on top in theory. The 460 has the edge overall. Torque/Hp is exactly that no matter how its made. Especially since it has near equal torque and more horsepower than the 91 Cummins.

 

Sure, you can get more torque with lower gearing. I could pull down a house with my weedeater with 1000000:1 gearing. What does that prove though? What practical demonstration are you going to do with gearing so low? I can't think of a situation where you wouldn't lose traction first (maybe an OBS retrofitted for a cog railway???)

 

It was basically over which trucks could tow more weight stock with less strain. As i said, with equal specs other than gearing, the lower ratios would come out on top but the guy wont acknowledge that saying diesels reign superiority period. Stupid argument, but at the time it was kind of relevant for both of us. Thanks for the input, I appreciate it.

 

The answer of who can tow more, is who has the highest LEGAL towing capacity. Anything more than that doesn't matter.

But if the argument is who's truck has an easier time towing, horsepower isn't a number I care about. Torque is, however. You have similar torque specs (assuming those numbers are both measured at the same place, and not one at the flywheel and one at the tire), but his torque is high as soon as he gets off idle. You have to wind your motor up to get that kind of torque. And if you're using the truck to tow every day, or close to it, I'd take a diesel over the 460 for longevity.

 

Yeah sorry bud, but the buzzin' half-dozen wins this one. I ain't a Dodge fan by any means (Ford > GM > Dodge > riceburners in my book) but diesels like that Cummins usually make their peak torque right off idle.

Try a Cummins vs Powerstroke war with him instead.

There is a reason that semi's, tractors, and pretty much any other equipment that is built to work all it's life is powered by a diesel engine, and yes durability is one of the reasons but also think of torque vs a gas engine of similar cubic inches. No contest there.

 

The old saying "horsepower doesn't pull a load, torque does" has a lot of truth in it, but strictly speaking it's not true. Torque can't move anything unless it's moving (duh!) and torque that's moving is horsepower. So strictly speaking, the engine with the most horsepower will pull more weight, or will pull the same weight faster.

However, the engine needs to be able to get to it's horsepower. A Formula 1 engine makes tons of horsepower at really high rpm. As long as you have the gearing to keep it at that high rpm a Formula 1 engine will out-pull a semi truck easily. But what happens when you start up a hill and you slow down a little? That peaky gas engine will start to fall off it's power curve and pretty soon it can't keep up.

This is where the truth in "torque pulls a load" comes in. If an engine has relatively low horsepower but relatively high torque it means (by mathematical definition) that it makes a lot of torque at low speed. That engine will still pull strongest at it's power peak, but as it slows down it is climbing back up it's torque curve. So as rpm goes down, torque goes up and horsepower stays pretty much the same. This flat horsepower curve is what makes an engine feel good at pulling, as it slows down a little it just keeps going instead of suddenly falling on it's face.

Of course another factor in how good a pulling engine is would be longevity. That Formula 1 engine would be a killer truck engine (assuming it had the gearing), but only for about 500 miles. By that time an engine that's wound that tight will be wearing itself out.

A big block gas engine will usually have more horsepower than a light truck turbo diesel, so strictly speaking the gas engine will tow more weight (or tow the same weight faster) if you keep the revs up. But the diesel with it's lower torque peak and flatter power curve will tend to "feel" stronger. And it will likely outlast the gasser by quite a bit (and burn less fuel doing it).

So which is best? Both can be argued to be better, so the arguements will never end (at least until the beer is gone).

 

You're dead on.

My whole statement, being based off of the ease of towing, was pointed at how low the engine is wound to move the load, with any luck making it last longer.

Your explanation using the Formula 1 engine is right though. It would be great up until it beat itself to death trying to move something, at say 7000RPM, where the torque might peak.

 

I'd have to side with the Cummins on this one. Having driven my cousins 6 speed Ram 3500, I can honestly say that it's got a lot of torque and serious pulling power. Being turbocharged helps immensely as well, any engine will see a tq benefit from one. Besides brute force, the diesel trucks will return far better mpg and longevity vs a big block gasser.

 

Yeah, but we're talking about a 1st gen Cummins. An old, non-intercooled, non-wastegated 6BT. 160HP with tons of turbo lag.

The 460 would probably pull with it, or even outpull it slightly.