Posted this yesterday and somehow I had put it in the Superduty forum by mistake and it just got all messed up by people responding with gas engines. I need the opionions of people that are using the 6.0 PSD.
I am thinking about getting the 6.4 next summer. It looks like the 4.10's may be available next year on the CC SRW. I'm trying to decide, if this is true, should I go for the 4.10's and the 20" wheel option or stay with the 3.73's and 18" wheels. It makes a difference of 122rpm at 65 mph. 1745rpm with the 3.73's & 18's vs. 1867rpm with the 4.10's & 20's. I tow a 30' fiver that weighs about 10K in the summer. Annually I tow about 2~3k miles and put about 15k on the truck total. Do I need the extra rpm for the load I pull or are the 3.73's more than enough? If the 3.73's are good enough for towing then it would should be better for mileage over the 4.10's for regular driving. Hopefully there are people here that pull a similar sized fifth wheel with their 6.0 and 3.73's that could enlighten me. What are your opinions on all this????

 

What do the wheels size option have to do with anything? The rpm's are affected by tire diameter and gearing ratios. Tire diameters being equal, your engine will spin faster with 4.10's.

You should be able to tow a 10k trailer with the diesel and 3.73's with no problems. Personally, I like the lower gears. (4.10 or 4.30's) But the newer diesel has a lot more power, so you should do well.

You say your trailer "weighs about 10K in the summer". Just curious...does it weigh less in the winter?

Seriously, I used 3.73's in my V10 and I went down to 4.30's with a big improvement in hill pulling power. I am assuming Alberta (lovely country) has a few mountains about that you would like to pull effortlessly. Gears count a lot. Diesels pull better than gassers, so the question is still unsettled.

My opinion...go with the lower gears (4.10) you won't ever regret it.

 

When I said wheel sizes I was refering to wheels and tires that come stock...275/70-18 or the 275/65-20. These are what I used to calculate rpm at 65mph or any other speed. I made up a spreadsheet that calculates speed or rpm. All I have to do is enter the numbers and it does it for me as I embedded the calculations in the spreadsheet.

That's funny, guess I worded that wrong...

On the most part Alberta is gentle rolling hills with the odd 6-8% grade. I only get into the mountains every couple of years. I am partial to going with the 4.10's and the 20" option, but I'm courious how it would effect the mileage. Thus is my delema. Power vs mileage. I would get the 3.73's if I knew for a fact it won't be kicking down on me every time a bit of wind blows up. If it will I would go with the 4.10's and eat the loss in mileage. I had a 96 with the 7.3psd and 3.55's and with the 235/85-16's that came stock it had a hard time staying locked in overdrive. I changed to 245/75-16's which helped with thier smaller diameter and it pulled much better. My current truck pulls like a horse, but the last two summers they have jacked up the cost of gas 25~30% when I do all of my towing. I end up spending a couple thousand on gas alone every summer just pulling the trailer. The cost of diesel fluctuates a bit, but on the most part stays fairly constant.

 

Stoner, I had 3.73 on my 03 6.0 and much prefer the 4.30 on my 06. The truck seems much more nimble around town. The only downside is traveling above 75 mph the mpg isn't nearly as good.

 

I don't think your wheel size/tires will make that much difference at all. At only 15k a year you are not going to see a lot in difference of cost. I favor the 4.10... or better yet 4.30 axle

That new 6.4 is a whole lot more powerful I am told. Even so, I went with the taller gears and soon regretted it when I upgraded my traler from a puny 6500 pounds to 10,000!! You just might get that same urge to get a bigger trailer, so be ready ahead of time.

I saw an article in a diesel shoot out where they used a Ford (vs Chevy 'Max vs Dodge Cummins). The Ford was a dually with 4.30's. They raved about the grunt power the 4.30's had.

I pull my 11 k trailer up to Utah where we have family and love to vacation. I pulled grades with the trailer and the new 4.30's where some diesels prefer to take the easier back roads into because they had 3.73's.

Unlike Utahtom, I have the advantage with the Gear Vendor being able to haul butt at less than 2 grand (rpm) at 75 mph in double over (4th gear overdriven).

Your big advantage is #1 diesel torque vs gasoline and #2) turbocharger to offset altitude power loss, which isn't your problem since the general are around Alberta is only in the 2300 to 2600 hundred foot range. Head west on 40 and you hit those big hills and go up to 7000.

Shoot, in Utah you start anywhere from 4500 feet in Provo or 5900 feet in Cedar City and then you climb into the mountains topping out at say 10,000 near Cedar Breaks or in the Uintas on the Wasatch. That's work!

 

Thanks, I usually cruise at 75 when I'm not towing as well. Haven't been down Utah way since I was a kid. My wife and I are wanting to do a loop down through Utah, Wyoming and Montana in the next couple of years.

 

subscribing....

 

Stoner, I don't know if this is going to help, but I will try. When I bought my new '05 in July of '05, it came with the 3.73's and the 17" wheel option. I found a sweet deal on some barely used 20's ($500) and put them on at around 5k miles on the truck. I have now pulled an 8k TT with both sets of tires on the truck, though I know that it wasn't all that broke-in with the 17's. I start pulling in Las Vegas (~1500ft) and end up at 7200ft in the Sierras. My towing mileage has been almost the same with both sets of tires (~10mpg each). The interesting thing is that my unloaded mileage has dropped with the 20's. I got as high as 21mpg at 70mph on a 380 mile trip, but I can't get anywhere near that anymore. I've also noticed that I'm pushing consistently about 3 more psi on the same stretches of road, which means the engine in straining somewhat. I've been seriously considering dropping to 4.10's to get me back into the powerband since the PSD just doesn't produce much power down low. I hate having to pull trailers at 75mph just to be at 2k rpm where there is definitely more power, and anything less and I feel like I am just lugging it. So after all that, I would recommend definitely getting the 4.10's if you get the 20's. Just don't forget that to replace the tires is going to be a lot more if you get the 20's, but they just look so good. I hope I could help.

 

DC3655
Thanks, that helps alot. I am going to go with the 4.10's if they do indeed have the option. I seen another post in a different thread that said the same thing.
BTW I was Stoner...changed name for obvious reasons. Had a brain failure the day I picked that name.

 

Not to make it harder Bueey...I have the 3.37's in my Harley with the 20"ers. Have pulled my 37' toy box over 12,000' passes and all over the Colorado mountains. Have had no problems at all. Good luck,I'm sure you'll be happy no matter!

 

Supposed to say Buddy, Jeeze...and I haven't even had a beer yet!!