Super Duty - PSD

[jbrnigan]

Looking for some input from Super Duty diesel owners.....
I will be ordering an '18 Super Duty - Power Stroke Diesel soon and am wondering about rear end gear ratios. I will be pulling my 29RKS - cat scales weight - 8500 lbs. What do you think is the best compromise between performance and economy - 3.31 or 3.55? (ps: buying a diesel not because I need it, but, because I can, and I want one)

[Magnolia Tom]

I’m not positive but I do not believe Ford offers 3.31 gears in the super duty. 3.55 would be standard with options for 3.73 and 4.10.

To answer your question, 3.55 gears do a really good job at balancing fuel economy and performance. You’ll have no problems pulling or stopping your trailer.

Edit-I see ford does in fact offer a 3.31. I would still opt for the 3.55. You never know, you may get a bigger trailer one day.
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[norty1]

My 06 has the 3.73 and has been a good choice for me.

[curver900]

3.55 min 3.73 preferable... you will not be able to calculate the difference in mileage... your cost is the buy and the immediate depreciation. if you are concerned about .1MPG then you can't afford one as you state ;o)


you will also get larger payload with the lower gearing...

[Midnightmoon]

I don't mean to take this off topic, but if you happen to be ordering an XL or XLT package truck, opt for the Operator Commanded Regeneration control. It isn't available on the upper package trucks but is a great option to have if you are ordering one.

[Wusaah]

I have an 04 F350 DRW with 4.10 gears. I am pulling a Seismic 4212 and man is it heavy. But I will say that I have no problem with the truck doing whatever I want it to do. I certainly won't win any races but it will "git up and go" whenever needed. I run 65 mph when towing and am probably getting around 8-9 mpg, but don't really care about those numbers. My truck is used almost exclusively for towing the Seismic. I would tell you that if you even consider going up in size on your rig in the future, you will appreciate having the 4.10 gears.

Rob

[oldmanAZ]

Like Norty1, my 06 has the 3.73 and has been a good choice for me. These are 2006, 6.0L diesels. I would think with the larger 6.7L diesel the 3.55 would be a good choice even if you decide you want a larger trailer in the future.

[repacs0103]

The 3.55’s are by far the most common, especially in terms of SRW trucks. That’s what I have in mine and I typically tow about twice what your trailer weighs with zero issues and power to spare.

As a sidenote gear ratios will not affect your payload capacity in any way, only tow rating/GCWR.


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[Loboclone]

Ditto on the Manual Regen option, I have a 2015 F450 with the XLT package. XLT with all the options, dual alternators and rapid heat option. I even put in the Resse fifth wheel from factory. I don't have to worry about derate due to Regen failure.
As for rear end gears I agree with the 3.55.
The F450 has only one option 4.30 gears, I get 9-10 mpg pulling an overloaded 4212.

[Force]

I have a '17 with the 3.55 Limited Slip but with only 2,500 miles it's not even broken in, and I'm getting 11 or so towing and unloaded if I manage my speed I can crack 16mpg all day long (almost 20 just putzing around town). Far far better than my 6.0L GMC ever did (a gasser, granted)

Can't say I would consider the 3.31's. I'd rather have the gear ratio meant for pulling vs. trying to eek out another 1 or 2 mpg

[TCNashville]

Originally Posted by jbrnigan

(ps: buying a diesel not because I need it, but, because I can, and I want one)

Good for you and get a black one. No problems towing our 10K TT with the 3.55's. All around fuel economy for us is in the 18/19mpg range. SRW's should come with the electronic locking rear differential as well. I don't think it's an option for a dually.

[jbrnigan]

Thanks to everyone for their input - looks like an easy decision - 3.55's

[DonaandDon]

Blue Jean is the best.