2talltechie

Ford is not posting their own tow numbers, at least not for the F150. The numbers come from the Society of Automotive Engineers (SAE). See SAE J2807.

Payload is a different issue, and not affected by the axle gear, which is what I am trying to decide on.

Thanks for the posts. I'm soaking it all in.

I may tow a modest rental travel trailer all of about 4 days this year. Maybe the same for the next couple of years, but retirement and more travel is likely. Would love to see more of the lower states, and possibly up north in Canada and Alaska. I'm thinking that the 3.55 axle would be an insurance policy for future tow requirements even though as of now, don't really need it.

Do you notice any extra noise, vibration, etc with the lower gears, or is it just that the little RPM dial goes up a bit and you fill up slightly more?

acadianbob

Fine, but it won't matter what your rear axle is if you have insufficient payload. That's all I'm saying.

brulaz

I really noticed a difference coming from an older truck. Some of that was all the sound deadening in modern trucks, but the rest was all the low end torque allowing the 3.7L EcoB to cruise at 1600 rpm when towing in 6th. That's with the 3.73 rear end.

With the 3.15 rear end that would be 1351 rpm, assuming it could maintain speed. My guess is that the torque (and HP) drop off at those low rpms would force it to shift into 5th. IIRC it drops fast under 1500 rpm, and reaches its peak torque at 2500 rpm.

We barely notice when it down shifts to 5th and the rpms jog up to 1800-1900 rpm (? not sure of the exact numbers).

But when it goes into a 4th and over 2000 rpm, it's definitely noticeable. Maybe because it doesn't happen that much.

A lot of this depends upon what you're used to, and what you can get used to. The 5L V8 should run routinely at higher rpms, that's where its HP is, and you get used to it (and even like it).

mvander

I'm would bet the diffference between 3:15s and 3:73s would be less than 1mpg. Get the more capable ratio and be done.

Also shop payload

PerryB

Get the lowest axle available. The benefit of having more useful transmission gears on the bottom end far outweighs any small economy difference at highway speed. I've owned over a dozen trucks or full sized V8 powered SUV's in the past 25 years and used every one of them for towing. I've never had one that felt over geared (4.10/4.56) but have had a couple that were under geared (3.31) and thought it to be a waste of an otherwise good truck. I couldn't care less about what its "rated " to tow. The seat of the pants difference is huge. You'll be much happier driving the lower (numerically higher) gears.

meaz93

If you really plan on towing anything with substantial weight within Ford limits....get MaxTow Package which usually comes with 3:73 gears(14's did)... and be done with it. I pull a 8k+TT and the truck lopes along in 6th gear....a lot! It's amazing and stress free traveling, especially when you hit those 6% grades -no worries. MPG's are very decent IMO. Unhook at campsite, and enjoy tooling around town getting excellent gas mileage...that's how it's done!