People always claim the ride is better with IFS, but I just don't see it or feel it. They know that they can't make the argument that it is stronger, so they try to make comments about the quality of the ride. Last time I checked, a pickup truck was built for towing and hauling, not fetching groceries. Nothing against those of you guys who use it for that purpose, but it shouldn't be designed for around town driving like the Chevy.

Did I mention that the new Dodge Hemi Diesel I-6 will have 2 front axles? One will be solid and 1 will be IFS.

 

I heard the new I6 hemi diesel rides like a feather even when it tows 50,000 pounds. Also, did you hear about the new tests for the Hemi Diesel... apparantly they tested it and it will last 10 million miles.......that's 9 million more than they claim their good for now!!

 

Will you be able to switch it on the Fly like the electronic 4x4??? That would be awsome

 

The low end torque of the PSD is good, but not as good as the cummins. As for the Cummins torque curve, if you go back three or four pages, I quoted a test article that stated everything I repeated about the Cummins torque curve.

As for the torque reaching clear out to 2900 rpm compared to the inapplicable graphs you saw, you have to realize, Cummins and Navistar both have to make these engines rev out a lot higher in a light duty application to be able to make the high horsepower numbers that rev crazy light truckers like to see. In heavy-duty applications, both of these engines are governed at 2600 rpm or less, depending on tune. Don't believe me? Go to www.navistar.com and look at their engine data.

As I've mentioned before, and I'm going to get back to, horsepower is a function of torque and rpm. The higher an rpm you can maintain a certain level of torqe at, the quicker you can get a job done, and thus, the higher the horsepower number is. That's what horsepower is. How quickly work can be done. It would take an such an unfathomable amount of torque at lower engine speeds to produce the horsepower that competitition has mandated necessary in this class, that it would just beat up drivelines and evertyhing. So, still needing huge power numbers for sales brochures, the light duty truck company specifies a higher revving tune than what the engine was really designed for so that it will be able to put up big horsepower numbers.

With regard to the Cummins having above 555 lb-ft at 2900 rpm, you're right. It's not close to that. It's closer to 590. I have tried to explain with cold hard numbers (an engineer's best friend) that the Cummins is, in fact, producing just shy of 590 lb-ft of torque at 2900 rpm, and you have chosen not to believe me. But I'll go over it one more time:

Horsepower and torque (when measured in lb-ft), the way they are defined, will always be the same at 5252 rpm. Below that, you will always have more torque than horsepower. If you know one of the numbers at a given rpm, you can calculate the other knowing these simple facts.

We know the Cummins has 325 horses at 2900 rpm. To calculate the torque at this point, we take 325, divide it by 2900, and multiply the result by 5252. This gives a torque number of 588 lb-ft, if I recall correctly. Torque, horsepower and rpm are undeniably interrelated. If you know two of them, you can find the third one.

And, while I'm at it, I'll reiterate my stance that if they were hitched to the exact same drivetrain the Cummins would be far better at getting a load moving, and depending on the overall gearing, could be better or worse at keeping it moving down the highway. If you were in such a situation to run the engines past 3000 rpm, the Cummins would fall on its face, but, even though you can, how often do you run your PSD past 3000 rpm? So in fact, even with the exact same drivetrain, the Cummins might be better off, if say, both engines were cruising along at 2400 rpm... because the Cummins would be closer to its horsepower peak, and would in fact, be producing more power and torque.

And again, if you geared the rearend of the Cummins truck proportionally to make both engines develop peak horsepower at the same road speed, the Cummins truck would lose its bottom end advantage, but still be able to do the exact same amount of work as the PSD, but with less engine wear.

One more thing, Marine Ironman, I find it funny that you are constantly tooting the horns simultaneously of wide powerband and transmissions with many gears. They reflect two different philosophies of doing the same thing. An engine with a wide powerband doesn't need to have so many gears. And a transmission that can always match a gear to what situation you're in doesn't need an engine with a wide powerband in front of it.

Finally on powerbands (and I've tried to explain this earlier too), since everyone likes to look at the whole system the fact that the PSD revs higher doesn't make any difference, if both trucks are geared properly for their engine. For example, if 1st gear in the PSD truck has it topping out at 20 mph at 3300 rpm, and 1st gear in a Cummins truck tops out at 20 mph, but at 2900 rpm, then it doesn't matter that the PSD can rev higher, as both engines can make use of their entire rev range over the same vehicle speed range.

Now I know that's not quite a realistic evaluation, but darnit, I'm just talking about engines. And besides, I don't give a lick about auto transmissions, personally... I'll talk about them with you all day long, but my only concern is how the trucks perform with a manual, and I think that they basically are the same, and in fact, according to a manual trans equipped comparo that I posted a few pages back, the Cummins had the nod in that arena.

EDIT: I referenced a couple of articles in this big long spiel, and they're on page 19, post #469.

 

I agree with Johnsdiesel here. I cant feel the difference either. IFS or leaf spring. Im glad Ford has stuck with the work truck idea in mind. Ford has the truck to fit anybodies bill. Is it me it seems like the newer Chevies 99 on up are lower to the ground than the older 88-98 series. I have no what there thinking was here. Put one of those nerf bars on and you sure dont have much clearance period. Ive seen plenty of those bent where they hit in a low spot. Geez if I wanted such low clearance I might as well be driving a car. It seems like Chevy is just really a city truck made for peoplle who really dont use a truck like a truck anymore. It seems like you do see more Chevies in the city than the farm. How could you get through a snowdrift with one of these low chevies. You wouldnt go through much. I always tell my Chevy friends get a real truck Get a Ford. Of course they dont like to here that.Sorry off the subject here. Like a poster said on here. Its sad when you cant tell the two wheel drive from the 4 wheel drive.

 

RE: IFS VS SFA OFF ROAD

This is kind of off-topic, and for that I apologize, but my mission here is to help other people know the truth about various things, or at least the truth as far as my feeble mind can perceive, and why I think what I do. So, with that said, I have to comment on IFS for off-road.

It's junk. Even bone stock, and in fact, especially bone stock, solid axles are much more desireable.

I don't want to go back and find the post, but I believe it was said, "how many rock crawlers do you see with solid axles?" Almost all of them, actually. Maybe on pro rock crawling competitions on TV, they have some megabuck independent suspension rock buggies, but that's not how it is here in the real world. You have to realize that those things were designed from scratch with a whole different purpose in mind than "ride comfort", or whatever makes GM think IFS is a good idea.

But, the vast, vast majority of off-road vehicles, at least as rocks and mud are concerned, use solid axles, and for good reason. With rocks, you can actually get better tire contact most of the time with a solid axle; I know it doesn't make sense at first, but consider this: If three wheels are on level ground, and one is over a dip, the one on the other end of that axle is going to be pushed up toward the body, because of the weight, which will, in turn twist the axle such that the other tire goes down into the low spot, giving you traction. In the same situation with IFS, your one wheel is pushed up toward the body under the weight, but that doesn't get transferred into any useful movement of the other tire.... not only that, but now that your front end is resting closer to the ground, your differential is either dragging or close to it.

As for mud, you need power, and brute strenth... solid axles are generally much more capable in the brute strength department. Also, if you approach a mud hole with any speed, and you hit it and slow down, a solid axle stays solid, but an IFS may compress enough that the differential hits the mud, which slows you down even more before your whole truck is even dirty....

 

I'm not by any means a safety ****, but none of that is a problem if you use a parking brake and chock the wheels like you're supposed to. And why wouldn't you be able to get it in gear? You know you have to push the clutch, right? Seriously, though, if it ever won't go into gear, just let the clutch out almost to the friction point for a second, the put it back in, this spins the guts of the trans enough to let you slide it on in.

And I have a hypothetical for you, since apparently you just trust the tranny... what about when the internal park mechanism fails, and your whole rig rolls into the lake? That'll teach you reliability.

 

As long as the ford SD's have solids, it'll be viewed as an advantage by the ford faithful. Same with the IFS and GM guys generally. Having owned both very recently, I agree that the driving experience is not much different except at hiway speeds (while towing) and over rougher terrain. My Ex was unstable at hiway speeds while towing but I'm sure that has more to do with the soccer mommed suspension than the SFA. In rough terrain, the IFS drives noticeably better/straighter. The chassis just gets less upset.

I drive offroad quite a bit for 3 months every fall chasing pheasants around MN and Iowa and both my GM's and Ford went the same places, snow drifts and all. But I never get aggressive about offroading. If the snow is deep or it's muddy, I don't push it.

No one I know lifts their trucks or goes rock crawling/mud bogging/sled pulling. It sounds like that must be popular in some parts of the country and perhaps the SFA is an advantage to those folks. But in these parts, it's pretty unusal to even see a lifted truck.

Bottom line to me is that there are advantages and disadvantages to both system but I'd own either. It does not factor heavily into my buying decision but I personally prefer IFS.

 

Its nice to know we have choices out we can get what we like. IFS has its place. Ford half tons have had it since 1980. GMs since 1988.

 

Well I simply cannt tune the radio in our Excursion on a rough gravel road at any kind of speed other than a Crawl. In a 3/4 ton Burb.... Same Road, No problem.

 

Yes, the guy that it happened to pushed the clutch, and his park brake was locked. So much for manual transmission reliability. Reason I know it happened was they had to call the fire dept. to come fish him out.

About your hypothetical, it wouldn't happen. #1 the Park function is the primary means of staying still, and #2 you mentioned the park brake, which is the second safety feature, so, in your frame of mind, it couldn't happen to an auto unless somebody robbed the transmission out while you were in the boat.

 

The Cummins is nothing compared to the I-6 Hemi Diesel!

 

Maybe but in a light diesel truck it is the broad power band of the power stroke that makes them such a joy to drive. If you will look at my dyno sheet on my gallery, mine makes over 500 ft lbs of torque from 1900 RPM to 3700 rpm The "sweet spot" of over 700 ft lbs runs from 2300 past 2800 which makes towing my car hauler at 80 mph effortless. The peak torque of 728 ft lbs is not as important as the average torque over the usable power band.

This is a stock engine and truck with a Predator tuner which really shows how much Ford can do with this truck without going back to redesign. If they let IHC go back to the original design which had digital variable valve timing, the potential for even greater usable power exhists.
By the way, like most 6.0 owners, I have never had a problem with my truck. Anyone who promotes otherwise is not truthful.

Eat Your Hearts Out Chevy and Dodge Fans!

 

I've just been reading some of the opinions on this thread. Some of you people are really ignorant about the 6.0. Why not go over to the 6.0 Forum and learn something factual?

 

I do frequent that board - often. What are some of these things that we are ignorant of?