Truck will be used as a daily driver w/ 35’s. Towing occasionally less than 10k.
what would be the better option?

 

I went with the 3:31 gears. So far, around 20 mpg. Absolutely would do it again. Pulls like a completely different 6.7L. Runs like my 08’ 345 KEM tuned 6.4L..
With the 10 speed and it’s closer gears, simply clicking from tenth to ninth gains you 200 rpm, so violet’, you have your lower gear if need be without the HUGE jump down like the six speed’s 6th to 5th

 

I have a 2019 F-350 with 3.31 gears and I tow a 15,000 pound fifth wheel all over the country. These trucks have huge torque and don't need higher gears unless you are planning larger wheels, etc.

 

Tires will be upgraded to 35”x12.5”

 

3.55s for sure....probably no mpg difference with 35s

 

If you are going to install larger tires go 3.55, but in the end like mptjelgin said in his post it probably won't matter. If you never have driven a diesel you're in for great surprise, one word TORQUE!

 

As your tire size increases over stock, so does the gear ratio. Of the two choices, start with the 3.55s as you plan on increasing tire size.

 

Can you still do 3.55 without getting the high capacity tow?

 

No you can’t. That’s my issue. I don’t want the $1500 up charge for that upgrade.

 

I would and did go with the 3:55s. I would bet the difference between mileage and towing is very very small. If I could have I would have ordered 3:73's as these have been the best all around gear sets for our shop trucks. But like was stated the diesel has so much torque and the 10 speed a wide range of ratios it is just not a major concern like it once was. Cj

 

2nd diesel. I traded a 2015 F250 Platinum on a Tundra and coming back for the diesel.

 

Sounds like I need to order the 3.55’s for the larger tires......

 

Tires at 34.1” is OE and ‘35s’ are actually 34.5”.

As long as you stick with the ‘35s’, or 285s in that height. I wouldn’t sweat it.

They did modestly change the gearing. I would actually be more worried about holding 10th than acceleration. .

 

Joe T,
Can you please explain the rational behind holding 10th? Say 10th gear is held at 55mph or higher, with larger tires, 10th gear would need to be above say 60mph. Is there a lock out in the transmission and shifting back and forth would cause excessive wear. Serious question.

 

I have the 3.31's in my '17 F250 CCSB, my son in law had the 3.55's. On a trip with him following us, our MPG's were < 1/2 MPG...

I wish I would have ordered mine with the 3.55's.