Rear end gears

[R&JS]

My hopes are to get a Montana 3120/21, sometime next year. I have been looking for a new tow vehicle and one of them was an F350 PSD, CC SRW with the 3:31 gear ratio, 10speed trans and 20" wheels. I really like the way it drove, plenty of power when not towing. The other was also an F350 PSD, CC, DRW. it had 4:10 gear. Whatever truck I end up with will also be an everyday driver, in Florida when we are not traveling. I wasn't thrilled with the 4:10 gear around town. The RPM's were noticeably higher in town and at highway speeds. I am curious about how the DRW with a 3:55 gear or the 3:31 gear on the SRW would do pulling in the mountains out west?

[AZ Traveler]

I have 3:55 gear ratio. No issue with our 3160 which was the predecessor to the 3120 with the exception of 10% grades which are fairly rare.

[Woodwork]

I have 331 with 3120 and I like it

[Harrisden54]

I have the 3:31 gear ratio on a 2019 F350CC SRW 6 speed Transmission. My trailer is about 15k lbs. No trouble pulling it on Hywy. 70 over the Rockies. I would think with the 10 speed tranny you will have no problems either.

[sourdough]

Originally Posted by R&JS

My hopes are to get a Montana 3120/21, sometime next year. I have been looking for a new tow vehicle and one of them was an F350 PSD, CC SRW with the 3:31 gear ratio, 10speed trans and 20" wheels. I really like the way it drove, plenty of power when not towing. The other was also an F350 PSD, CC, DRW. it had 4:10 gear. Whatever truck I end up with will also be an everyday driver, in Florida when we are not traveling. I wasn't thrilled with the 4:10 gear around town. The RPM's were noticeably higher in town and at highway speeds. I am curious about how the DRW with a 3:55 gear or the 3:31 gear on the SRW would do pulling in the mountains out west?

I'm a Ram guy and haven't driven a Ford with the 10 speed but I would have thought the 10 speed would really improve that "high rpm" feel. I went from a Ram 6 speed to 8 speed and the difference in rpm is very noticeable. I cruise at the same rpm as the old 6 speed but have much more control over the power band with the new ratios. I would have thought the 10 speed would do the same thing.

[mlh]

These new trucks are so powerful you can get by with higher gears. The truck will probably use a lower gear most of the time but with 10 to choose from you would never notice it unless you had pulled your camper with a truck with lower gears. Even then it will be pulling about the same RPMs.
Lynwood

[Slow Hand]

3.31 with the 6 speed and mine pulls fine. I was completely surprised. plenty of power. I also get decent fuel millage towing about 12

[RMcNeal]

Mine is the 3.55 gear ratio. It does fine and as I understand it, the 4.10 will use more fuel given the same load and conditions. Unless you are really pushing a weight limit, I'd stay with the lower ratio.

[makeithappen]

Well, I have a 2020 f-350 DRW w/4.10 rear. & 10 speed. Right now empty mixed driving 14/15 mpg. I run 2000/2100 rpms at 75 on highway. I have not towed yet as my 2021 3120rl will not be here until dec. I will post when I tow with it, but I already know it will be awesome. To me more gear is always better, the mpg's between 3.55/4.10 is not a big deal. As far as DRW I like it, and have no problem using it as a daily driver. I think this is a preference thing, just like the floorplan of a 5th wheel that you might pick. You can only get 3.55/4.10 in DRW.

[Slow Hand]

Actually the gear ratio makes no difference. The transmission makes up for it with the gears in it. If you took a truck with 3.55 gears and swapped them out for 4.10's you would notice the fuel difference just like the feel of the power of the truck. What ever rear gear you have will do just fine in the truck. I have a 4x4 and it would get expensive to change out my gears. When you get to order a truck and you get to chose which gear you want i bet you get a transmission to match that gear set.

Another thing with a SRW truck you may not be able to order 4.10 gears. What ever gears that come with the truck you will be fine. My truck will move my 3280 RL without even stepping on the gas.

[BB_TX]

I have a 2012 F350 with the 6.7, 3.55, and 6 speed transmission and it tows the mountain passes of Colorado with no problem. And cruises at 70 towing on rolling terrain in cruise and rarely ever drops out of 6th. I would think the 3.31 and 10 speed would also have no problem.

[JABURKHOLDER]

Torque gets you moving, horsepower keeps you moving. Rear end gears have nothing to do with the horsepower rating but has everything to do with how much torque is applied to get you moving. On an engine dyno, horsepower and torque are measured. Max torque is generated at a much lower rpm than horsepower. This is especially true in a diesel engine. Max torque is usually in the 1500 - 2200 rpm range. The rear end gears affect the rpm, the taller (higher number) the gear, the higher the rpm. The whole idea with the right rear end gears is to get you moving with the least amount of effort from the engine. A higher gear ratio does that by getting the engine rpm in the optimal torque range more quickly. The transmission controls all of that by picking the right gear to keep you in that optimal rpm range. The Tow/Haul mode on the Ford does exactly that. It keeps the engine at a slightly higher rpm, to maximize torque, for a longer period during shifts to get you moving. Ideally, you would research where your engine generates its max torque, find out the gear ratios in the transmission, do the math for the final gear ratio (transmission gear X rear end gear) and see what rpm ranges are generated. BUT, you're not building a race car. Almost everything in vehicles today is a compromise. Fuel economy, power, cost, etc.

All that being said, If I were in your shoes, I would go with the 3.55 gears. A very good compromise for your towing needs and daily driver.

Personally, my F350 has 4.30 gears and moves my the truck and RV (3791RD) (approx. 24500 lbs combined) at idle.

Just my long winded 2 cents.

[Dave W]

I would probably opt for a 3.55 ratio final drive - even with a 10 speed. My '11 with 3.55s does just fine though starting from a dead stop at the bottom of a nasty hill can make it a real slow climb until the truck/trailer get a head of steam. Don't know if that 10 speed has a lower initial ratio then my 6 speed though which may allow for a better start on a grade

[mazboy]

don't get the 4.10 the others will be fine. stay with SRW

[whiterose]

10 speed is the way to go. The higher three ratios are overdrive and the lower ratios are lower allowing the use of lower numeric rear axles.

[Leonard R.]

Hi,
I have a 2020 3120 and pull it with a 2017 Chevy Dually diesel with a 3:55 rear. I use it as a daily driver as well and no issues. In fact, it is just about perfect for me! I read that the Duramax is a little quieter than the Ford, but probably just your preference there.
Best of luck on your truck.

[Sac Colorado]

Hi Rick,

I pull a '13 3100RL (probably a hair less than 14,000 loaded) with a '17 RAM 3500 w/ a short-bed, 18' wheels, SRW, 6.7 Cummins with 3.42 rear-end, an Aisin 6-speed transmission, and the truck GVW is 11,700. We live in Fort Collins, CO and regularly tow in the mountains. I've pulled the RV over Loveland Pass near Vail a couple of times on the way to Moab/Arches, up to Yellowstone, a bunch of times up to Mount Rushmore (not quite as much grade as heading due West) and "just for fun" pulled over Wolf Creek Pass on the way to Durango, CO - that one is really steep and at altitude! Towing in the mountains with a 3.42 rear end - I've never had any problems moving the load up the hills and I've always felt safe with my exhaust brake and making sure I always control my speed on the decent. The real beauty of the 3.42 is 9 - 11mpg in the mountains towing and unloaded on the flats (heading east back to Wisconsin from Colorado) I regularly get 25+ mpg. Hope that info helps, Sean

[Jritz]

I have a 2019 f350 srw with 355 and I pull a 3855br goes GVWR is 16900. I’ve put 20,000 miles on both the truck and trailer in the past year. Love love love it!!
Went up and down Tioga Pass outside of Yosemite like it wasn’t even there.

[laverdur]

My Monte is packed to near GVWR on a 3-month trip. My TV has the 3.31 axle and it does not know what a hill is. It takes 8% grades in stride with little reduction in speed. A 10% grade will slow me down but I never worry about not making it to the top. The fuel economy is nice with the 3.31. The 10-speed tranny should only make it better. I'd take a hard look at what 20" wheels (tires) do to the TV GVWR. When I ordered my TV 20" wheels resulted in 10,000 GVWR vs. 11,500 GVWR for 18" wheels.

[RBGALL]

Check the door sticker. What is the GVWR and GCWR of each truck. The gears make all the difference of what you can tow!