3.55 vs 3.73 gears
12-11-2010, 09:24 AM
#11
You could be right, as I was only guessing. I moved from 3.23's in my Cobra to 3.73's and saw about a 600 RPM jump on the freeway -- but that was a lot bigger move gear wise, and it had only a 5 speed......
On a side note, the 3.73's and the 3.53's are rated the same on the window sitcker for MPG. PART of this might be that on very moderate grades, the engine (with the 3.73's) is higher in the torque curve just enough to stay in OD and not have to downshift. I've noticed when towing my TT, when I drive at a bit higher speeds, its able to stay in 5th and 6th more. When I slow down, the trans is constantly downshifting a lot more.
On a side note, the 3.73's and the 3.53's are rated the same on the window sitcker for MPG. PART of this might be that on very moderate grades, the engine (with the 3.73's) is higher in the torque curve just enough to stay in OD and not have to downshift. I've noticed when towing my TT, when I drive at a bit higher speeds, its able to stay in 5th and 6th more. When I slow down, the trans is constantly downshifting a lot more.
12-11-2010, 10:22 AM
#12
Senior Member
I wish I had the 3.73s.
I have the 3.55s and they were fine until I put on larger 33.26" tires. Now this itself isn't horrible. The problem lies in my many trips thoughout the year to Flagstaff, AZ. The drive is quite hilly and with the bigger tires my tranny is always downshifting.
Like a couple members stated, terrain has a lot to do with it as well. If you're in a hilly or mountainous region, the extra gearing will be most welcome in power and mpgs.
And let's not forget, we all wanna look good. So those wimpy stock tires they give us usually aren't enough. But bear in mind that if you upsize, you're essentially reducing the gear ratio as well.
I have the 3.55s and they were fine until I put on larger 33.26" tires. Now this itself isn't horrible. The problem lies in my many trips thoughout the year to Flagstaff, AZ. The drive is quite hilly and with the bigger tires my tranny is always downshifting.
Like a couple members stated, terrain has a lot to do with it as well. If you're in a hilly or mountainous region, the extra gearing will be most welcome in power and mpgs.
And let's not forget, we all wanna look good. So those wimpy stock tires they give us usually aren't enough. But bear in mind that if you upsize, you're essentially reducing the gear ratio as well.
12-11-2010, 03:41 PM
#13
355
I have the 355LS I think for the most of us this is the way to go it can tow 9500 with my 2010 crew 6.5 I have towed my 1963 Galaxie from FLA to NJ with no trouble at all and that's a 4000 car and a 2000 trailer it's good for highways and ok for light off roading, If your going to change tires and lift it and pretend your rob millen then go with the 373 heck that might not be enough.
12-11-2010, 04:19 PM
#14
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when test drving the two, i couldn't tell the differenece. i got the 3.55's and have been pleased. I tow my CJ with it and it does just fine, I've towed it up and over passes as high as 10,500' and it has power to spare. the milage averaged (hand calculated) 13.9 from the front range area over to the western slope and back. no regrets not getting the 3.73's.
12-12-2010, 10:00 AM
#16
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I've got the 3.55 and I've had at least 13K behind me with a two axle trailer and two 4K pound concrete skids ontop. The truck handle fine, but I was babying it because I didn't want to rack the frame or screw anything up. Does this mean that the 3.55 has to work harder and could prematurely fail? I've thought about going to 4.10 but when I bought the truck a lot of people advised me to use the 3.55 because I'd get better mpg on the highway. Maybe this is also why some exhaust kits drone and others don't, if the rpms at 70-75 are 500 less like others estimate, that would be the reason to go up also. I think these trucks get drony at the 1800 to 2000 rpm range, and if you could change that sweet spot, maybe drone would be eliminated as well.
10-23-2014, 09:42 AM
#17
Trying to order a 2015 Platinum and Ford will not let the dealer order it with 3.73 gears as it apparently comes with 3.55. I do tow a 30' travel trailer and could probably live with the 3.55's but I also want max payload and max towing. It gets complicated trying to get what you want.
10-23-2014, 11:16 AM
#19
wait. what?
I had 3.55s on my 2010 5.4L King Ranch and I now have 3.73s in my 2014 King Ranch max tow. I agree that the 3.55s really made it a dog with larger tires. I would say for a fishing boat you would be fine with 3.55 as long as you don't go to a larger tire but I love my max tow package because of the mirrors and I easily get 19mpg on the highway with taller and heavier tires.
10-23-2014, 12:02 PM
#20
I had 3.55's on my previous 2002 SuperCrew FX4 5.4L with larger than stock tires and it hurt driving around our hilly terrain here. Plus, before going to larger tires, I always picked up and hauled 1 ton of pellets for winter use at least 4 times a year. Yeah, it was over weight a little bit but drove OK. Now my new 2013 SuperCrew FX4 with 3.73 gear ratio is a lot better hauling the 1 ton payload I throw in the back. 3.5L Eco engine does a great job too and the truck accelerates much better than the 02 with the 3.55's I had.
I plan on going larger diameter tires after the originals wear out, maybe 1.5" and when shopping for my new truck, I made sure the dealer knew I was looking for 3.73 gears and not 3.55 or 3.31. If 4.10 were not so expensive to upgrade to, I would have opted for them.
I didn't buy my truck for gas mileage savings, I bought it for its luxury and its ability to haul anything I put in the back that will fit.
I plan on going larger diameter tires after the originals wear out, maybe 1.5" and when shopping for my new truck, I made sure the dealer knew I was looking for 3.73 gears and not 3.55 or 3.31. If 4.10 were not so expensive to upgrade to, I would have opted for them.
I didn't buy my truck for gas mileage savings, I bought it for its luxury and its ability to haul anything I put in the back that will fit.
Last edited by Keith460; 10-23-2014 at 12:04 PM.