Ford 3.31 or 3.55?

mich800 wrote:

720Deere wrote:

OpenRangePullen_Ford wrote:
A 3.31 doesn't belong in a truck, its useless. Get the 3.55 or bigger for sure, It will give you more useful power.

That's funny because not that long ago people like you said that 3.55 was no good in a truck and not long before that they were picking on 3.73. When diesel motors had 200 hp and less than 400 lb/ft, gearing made a bigger difference than it does now at 400/800 and beyond.

I have 3.55 with the 20" wheel option and towing 16,000 lbs is no problem at all. I have no problem maintaining greater than 62 mph in the mountains which is extraordinary compared to trucks just a few years ago. I was initially leery of 3.31 when they were first offered, but after 3.5 years of experience with the 3.55, I would not hesitate to get 3.31 with 18" wheels. If you intend to install larger tires at some point, I would stay with the 3.55, but 3.31 with stock 18" tires is going to net you the best fuel mileage and will still perform the same as a 3.55 truck with 20" wheels.

It depends, do the new Fords have the four speed with overdrive or are they still three speeds.



:)

They have a six speed with 2 overdrive gears.

720Deere wrote:

Lynnmor wrote:
I believe that you will find the 20" tires handle less load than the 18"

Can you expand on this theory? My 20" tires as well as every other 275/65/20 tire I have ever seen are rated at 3750 lbs. 18" tires typically max out at 3640. I will also add that with 20" tires the RAWR is 7,000 lbs on an F350. I don't recall seeing a truck with 18" wheels rated that high.

Yes, I see that you are correct after comparing the two. When I ordered my truck 3 years ago, I was given a lower rating for the 20".

Lynnmor wrote:
I have the 3.55 with the 18" wheels. Works great. I believe that you will find the 20" tires handle less load than the 18"

Diesels spin slower than gas engines, so pay no attention to comparisons of gear ratios between the two.

The only thing you'll notice between the two tires is the price tag when it comes time for new tires. :W

Lynnmor wrote:
I believe that you will find the 20" tires handle less load than the 18"

Can you expand on this theory? My 20" tires as well as every other 275/65/20 tire I have ever seen are rated at 3750 lbs. 18" tires typically max out at 3640. I will also add that with 20" tires the RAWR is 7,000 lbs on an F350. I don't recall seeing a truck with 18" wheels rated that high.

My trailer is relatively light for a 350. I have 3.31. Power is enough to get me up the hills at the speeds I prefer to travel (65mph). YMMV

I have the 3.55 with the 18" wheels. Works great. I believe that you will find the 20" tires handle less load than the 18"

Diesels spin slower than gas engines, so pay no attention to comparisons of gear ratios between the two.

Javi1 wrote:
Diesel...

The 3:31 is only available with 17" or 18" tires the rpm differential is minimal between them and either will work just fine for pulling any load applicable to a SRW F250 or F350. If you want the 3:55 ratio you will need to buy a truck equipped with 18" or 20" wheels. However because of the overall increase in diameter when going to the 18" and 20" tires the 3:55's deliver an almost nil increase in performance over the 3:31.

My '12 diesel has 17" tires and the 3:31 ratio..

A dually F-350 comes equipped with 3:73 ratio...

3.55 ratio is available with 18" wheels but it is mandatory for 20" wheels.

Javi1 wrote:
Diesel...

The 3:31 is only available with 17" or 18" tires the rpm differential is minimal between them and either will work just fine for pulling any load applicable to a SRW F250 or F350. If you want the 3:55 ratio you will need to buy a truck equipped with 18" or 20" wheels. However because of the overall increase in diameter when going to the 18" and 20" tires the 3:55's deliver an almost nil increase in performance over the 3:31.

My '12 diesel has 17" tires and the 3:31 ratio..

A dually F-350 comes equipped with 3:73 ratio...

^^^^ This. As my dad would say, 6 or one half dozen of the other. Pick the tire you want and the gear will come with it.

To those that say gear X is not big enough, bla, bla, bla.......have you ever towed with 400 HP and 800+ ft/lbs of torque? I would guess not! :R

720Deere wrote:

OpenRangePullen_Ford wrote:
A 3.31 doesn't belong in a truck, its useless. Get the 3.55 or bigger for sure, It will give you more useful power.

That's funny because not that long ago people like you said that 3.55 was no good in a truck and not long before that they were picking on 3.73. When diesel motors had 200 hp and less than 400 lb/ft, gearing made a bigger difference than it does now at 400/800 and beyond.

I have 3.55 with the 20" wheel option and towing 16,000 lbs is no problem at all. I have no problem maintaining greater than 62 mph in the mountains which is extraordinary compared to trucks just a few years ago. I was initially leery of 3.31 when they were first offered, but after 3.5 years of experience with the 3.55, I would not hesitate to get 3.31 with 18" wheels. If you intend to install larger tires at some point, I would stay with the 3.55, but 3.31 with stock 18" tires is going to net you the best fuel mileage and will still perform the same as a 3.55 truck with 20" wheels.

It depends, do the new Fords have the four speed with overdrive or are they still three speeds.



:)

Diesel...

The 3:31 is only available with 17" or 18" tires the rpm differential is minimal between them and either will work just fine for pulling any load applicable to a SRW F250 or F350. If you want the 3:55 ratio you will need to buy a truck equipped with 18" or 20" wheels. However because of the overall increase in diameter when going to the 18" and 20" tires the 3:55's deliver an almost nil increase in performance over the 3:31.

My '12 diesel has 17" tires and the 3:31 ratio..

A dually F-350 comes equipped with 3:73 ratio...