LH:

The PSD, gearing wise, can go 52 in 3rd gear. Engine torque-wise, it will too. we showed about 3500 rpm at that point. Redline on the PSD rpm-guage is 4200 rpm. I took a stab, looking at the published PSD torque curve, that it appeared to be more than 450 ft-lbs, but I used 450 for the calculation. Yes, you're pushing the truck to the max at that point.

Why am I not showing Horsepower? Because I'm calculating work, in order so you could come up w/ a theoretical actual load of resistance.

E.g.: Let's take Cummins at 1600 rpm
Work = Torque x RPM x time
Work = 600 ft-lbs x (1600 rpm x 6.28 radians/rev) x 1 minute
Work = 960,000 ft-lbs-rev (x 6.28 radians/rev)
Work = 6,028,800 ft-lbs (keep in mind this has transpired in one minute of driving)

What is the load? First you must know the distance you went in feet: Well, at 55 mph, you have traveled:
Distance = 55 miles/hour x 1hour/60min x 5280ft/mile
Distance = 4840 feet

And therefore the load is:
Load = 6,028,800 ft-lbs / 4840 ft = 1245.6 lbs

What does that mean? Is it the weight in the trailer? No. It is the weight in the trailer times a coefficient of friction for the axle ... PLUS ... the wind resistance of the truck and trailer ... PLUS ... the internal resistance in the truck's drive train (bearings, etc).

So, (I'm just going to make up numbers), we might have the following:
300 lbs of wind resistance
200 lbs of drive-train resistance
745.6 lbs of trailer weight times the coefficient of friction for the trailer bearings

What is the trailer weight? Well, if the coefficient of friction for the trailer is, let's say, 5% (just pulling out a number), then we have:
Trailer weight = reisistance load / friction coeffficient
Trailer weight = 745.6 lbs / 0.05
Trailer weight = 14,912 lbs

In reality, I would imagine the coefficient of friction for a trailer is less than 5%. You could design a special hitch instrumentation, which would measure total trailer resistance (wind plus weight on the axle) to find out. Then you'd have to stick the trailer in a wind tunnel, find out the wind resistance and subtract that. That would give you the trailers coefficient of friction.

In Summary, I computed the Work per minute for each step, that is going on. I showed the 6.28 rad/rev, but did not multiply it, because I don't need to in order to make the comparison (i.e. do less math). But if I wanted to know the actual resistant load in lbs ... multiply times 6.28 and divide by 4840 feet for each step. Since it's not the trailer weight ... I didn't want to confuse people, and get 1,000 posts about how I'm showing "too low" of a load, and yadda yadda with a bunch of ladies from the forum popping in. The load, once again, is the resistance to being towed, not the actual GCVW.

SOMEONE SEND ME THE FORD MANUAL GEARS, AND I'LL DO THAT SCENARIO. AND I WILL BE DOING THE DURAMAX OVER ON THE RICE-BURNER VS. USA THREAD.

Ironman

 

Hey, give me a break. I've given Ironman and everyone else the utmost respect. I'm not being a jerk, just trying to help him sound professional. And if you go back to about halfway through the "most durable" thread, i think I was the first person to start getting into calculations - regarding hp vs. torque at rpm. Maybe not, but please do not imply that I am afraid of calculations. You know not, my friend. And for the last time, the only truck I own is a ford. The whole point of all these hundreds of pages is accuracy, and I'm just trying to help.

 

OK, now that we got that all taken care of..............back to this very...
L O N G.... thread

 

Its a null point MI. Two in one hand 3 in another but it all adds up to the same thing. I figure it is possible for the PSD to tow at 3500. It would really depend on the load. I have heard that it does not actually go above 3600 rpm even though it says 4000. I believe there is no torque after 3600 but I cannot prove it. It falls very fast after 3400. Move the speed up from 52 to 55 or 56 and its outta both of their reach.

Best way to find out. Go do a top speed test without the speed limiter. See where it stops. This is a very high load for an engine. Moving a truck with the aerodynamics of a billboard down the road at over 100 mph will take a lot of effort on the engines part. You will find where there is no longer enough force to pull a heavy load. I would speculate that it would probably run out of ghusto around 3450 3500 rpm. 3600 seems to be the end of the road. Oh 4.10s wont work. We need 3.55s. Puts more of a load on the engine. 4.10s cannot go over 100.
3600 isnt an arbitrary number. It is a number that Ive read of from PSD owners as the highest they have achieved with the auto. You could tell right a way with a manual where it runs out of steam. I dont exactly have access to one. I doubt my buddy with the 6.0 is gonna want me doin a buck 20 in his truck.

Once again. I cannot forsee any condition that would pull one of these torque monsters with a towing gear rearend down into second on the highway. Where most of us do most of our towing. So in a real world aspect. It doesnt really apply. Well it does apply but not often. If one has a lower top speed in a gear. It can tow more load. If it has a higher top speed in a gear in will tow less. Because they can both do the same amount of work in one minute. You can gear the PSD to match the Cummins towing or vice versa. 325 to the ground will move quite a bit of weight. More than I can pull. And Ive towed more weight than either the new cummins or PSD are rated for. It was in a na IDI and I never slowed down below 45mph on a very twisty and narrow 5-6%. Now with 325hp. I would be a speed bump to you guys.

 

LH:

• The 4.1 or 3.73 makes no difference in this analysis. All this shifting occurs at the same points, and the work outputs of the engines are identical. The rear-end simply gives you the actual MPH. It will be higher for the 3.73 (35 mph where the Dodge ended) and lower for the 4.1 (32 mph where I had it). I only used the rear-differential to give you a ballpark idea of the speed
• Secondly, towing something at ~55 mph is VERY applicable. The "LOAD" in this scenario can simply represent towing your 10,000 lb camper trailer and fully-loaded truck ... and heading up to the Rockies. When you first downshift ... you have entered my scenario below.

The Ironman

 

Your math explains a lot about your posts. Two does not equal three.

 

It is not…. impossible to believe, that two members here... could find a way to convince you it does

 

Not on a math board but in gearing it certainly can. The Dodge Cummins 48E is a 4-speed auto. The Ford PSD TS is a 5-speed auto. On the Dodge auto each gear is rated to go a higher MPH before it changes gears(since it only has 4). Therefore the Dodge Ram Cummins in 2nd gear can go nearly as fast as the Ford PSD in 3rd gear! In extreme example the Lamborghini Diablo doesn't have to switch to 2nd gear until after 60 mph. I don't know about you but my little car switches to 3rd before 60 so in this case 1=3. Of course you can't get a Lamborghini with an auto but there are extreme exotics with autos that have similar gearing.

 

That's one of the largest advantages that the PSD has, a 4-speed auto does not equal a 5-speed auto. Certain ratios may line up or be close, but 4 does not equal 5. The last math course I took was an undergraduate class for non-majors about 10 years ago and I can still figure that out!

 

Exactly thats why I can't wait til they get the 5-speed auto in the Dodge and then the Cummins would win in a race for the top of the hill.

 

It's just too bad for Dodge that Ford and GM are already working on a joint venture for a 6-speed auto.

 

Lower wheel speed equals more torque at the wheels. Regardless of hp and work per minute. Torque at the wheels it what keeps that sucker rolling down the road. If you have a lower top end. You will logically be able to tow a heavier load. So in the real world of towing 3.73 vs 4.11 is all the difference in the world. Specially where you are at in hp at 65mph. The two will be very different. The 4.11 will have access to more hp at 65mph.
A hp is a hp. If two rocks weight 20lbs and 3 rocks weigh twenty pounds. 2 can be equal to 3. Thats what I meant. Not specifically rocks just that 325 hp will do 325hp of work whatever gear or transmission you use. Each will tow better at different rpms or different speeds in different gears. In the end. Its still almost 1.1 million lb ft per min. One does it sooner the other later. Still the same. Other than holding a gear. With a cvt their performance would be identical.

 

People turn on the lights please. Its not the gearing that lets the PSD win, its the higher power band. As it stands, the Dodge can't win with a 4 or a 6 speed and a 5 speed is not going to be the magic pill. The dodge either needs to increase the power even more or move the powerband higher.

 

LH: In my computations, the torque is already accounted for in the work/time number (ft-lb-rev/min). Once you divided by the distance traveled, the lbs of force comes out. Distance is more w/ the 3.73, and the lbs less. Distance is less w/ the 4.10, and the lbs more. But the work is the same. Remember when I compared Cummins HP to Ford HP ... one went faster w/ less and the other went slower w/ more ... in that case, the work was constant.

Here ... my analysis is a true apples-to-apples. The speed is held constant. Notice each of the trucks are NEVER capable of the same amount of work while at identical speeds. The corollary is that if held to identical work potential ... their SPEEDS are NEVER the same. Thus, we must compare the first case (same speed).

The magazines go for the second case (same load, who is the fastest i.e. different speed).

Ironman

 

Terry ... excellant. Well said. Yes, you are exactly correct. The Cummins could have 20 gears, all changing instantaneously. It could still not beat the PSD in my constant-speed increasing-load scenario.

It'a all about how far out the power extends up the RPMS.

Cummins/Dodge literally has thousands of good, trusting men duped into thinking low-end-torque is King. Low end torque was made for one thing: Engaging mucho torque as far down near idle as possible, because ALL they had were manual transmissions. Of COURSE you want low-end torque for that.

But those days are over .... if you want antique tecnology ... buy a Cummins/Dodge/5600.