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3.15 axle with the new 10 speed trans. equals 3.55 axle with the 6 speed trans.
With my '13 F150 3.5 EB 3.55 having just surpassed 100k miles, I started glancing at what's available these days. It is my only caged vehicle, I haul grandchildren, I occasionally need to squeeze it into a parking deck, and I tow a toy hauler that at various times weighs 6600-7200 lbs. Therefore the 3.5 EB Supercrew 5.5 ft. bed 145" wheelbase configuration is the one that best fits my needs.
I notice that for '17, only two axle ratios are available for that configuration with the 3.5 EB, the 3.15 and the 3.55. In '13 it was available with four axle ratios: 3.15, 3.31, 3.55 and 3.73. I ended up with a 3.55. The spread from 1st to 6th on the six speed is 604%. The spread from 1st to 10th on the ten speed is 744%.
I also note that the GCWR for my '13 3.55 six speed is 15,300 with a max trailer of 9,800, whereas the GCWR for the '17 3.15 ten speed is 15,800 with a max trailer of 10,700. The advantage is the 10 speed transmission in the '17, plus the '17 has a little more power. They have almost the exact same first gear final drive ratio.
My current wet and loaded camper weighs 6,640 (68% of 9,800 max trailer) which results in a GCW of 12,500 (82% of the GCWR) and the '13 tows it with no sweat. It's at 94% of GVWR, having used up 71% of its payload. I'll be looking at the 3.15 axle with the 10 speed for the next one to tow as well as the 3.55 six speed and get a little better highway mileage when not towing (19% fewer revs per mile in high gear). I give the Ford engineers an "attaboy" for this one.
Last edited by atwowheelguy; 06-08-2017 at 12:50 AM.
Not sure where you were going with this but as a 5.0 owner, that 3.15 + 10sp would be vomit inducing. 1200rpm at 70mph or something
I was looking at getting started in first gear with a 12,500 lb. rig, not 70 mph. I would have thought I would never have considered a 3.15 axle for towing a camper. Just saying that the numbers say the 3.15 ten speed will get the rig moving from stopped just like the 3.55 six speed does. Same first gear final drive ratio. The 3.55 ten speed is now geared lower than the 3.73 six speed was. It would be the equivalent to a 3.99 with the six speed.
I like the 3.5 EB 3.55 six speed, so I see no reason why I would not like the 3.5 EB 3.15 ten speed. Quiet towing with plenty of low rpm torque. Looks like the ten speed makes up somewhat for fewer rear axle ratios available. Hope I don't vomit. The 5.0 in that configuration comes with the 3.31 or 3.55.
Last edited by atwowheelguy; 06-07-2017 at 08:50 PM.
I just see that as the 3.55 is even that much better down low. Top gears still more useable with the 3.55 when you are talking about a 12,000lb trailer
I think you are on the right track. Overall, you should see similar performance/mileage while towing and better mileage while unloaded.
I have the 3.73 in my 5.0 and it would be better to have the 3.31 with the 10 speed.
You're fooling yourself. Get the 3.55's. You still have more overdrive than you'll be able to use towing. Even with 3.55's you're going to find it in 8th or 9th a lot of the time on the highway.
I just see that as the 3.55 is even that much better down low. Top gears still more useable with the 3.55 when you are talking about a 12,000lb trailer
Not talking about a 12,000 lb. trailer. Mine's 6,600 lbs., 62% of the '17 3.15 3.5 EB J2807 rating of 10,700. Woe be unto the poor soul who tries to tow a 12,000 lb. trailer with a standard payload F150.
What I have now performs well. The numbers say the new 3.15 ten speed 3.5 EB will perform equally as well. Good enough for me.
You're fooling yourself. Get the 3.55's. You still have more overdrive than you'll be able to use towing. Even with 3.55's you're going to find it in 8th or 9th a lot of the time on the highway.
Except that the 3.55 only comes with the Max Trailer Tow package for a '17. That really narrows the field when shopping. I'm towing a 6600 lb. camper now very well without a Max Trailer Tow package (3.73 axle in '13) so I don't see why it would be required with a '17 truck to tow the same camper.
85% of the miles put on this truck will not be towing anything.
I'm thinking of upgrading my '13 EB with 3.73 rear end to the new 3.5 EB. The gear ratio charts posted here really help. I'm thinking the 3.55 might be best for me. Most of my use is pulling a 27' Airstream that weighs about 7700 pounds loaded.
My big question is where does the extra 50 ft./ lbs. of torque come in with the new engine vs. the old one.
Has any one seen a torque curve graph for the new engine?
06-07-2017, 03:21 PM
3.15 axle with the new 10 speed trans. equals 3.55 axle with the 6 speed trans.
