2002 F-250 5.4 had 265/75/R16's from the factory which are the "bigger" tire upgrade.

I put on 285/75/16's quite a while back and have been unhappy with the take-off ever since. Sure, it's not a HUGE difference but the shift points are definitely different. I notice the loss of gearing mostly when towing.

I have seen a LOT of guys running 3.73's get recommended up to 4.11's.

I currently run 4.11's and according to the charts, I should be running 4.30's with these tires. However, do I want to run 4.56's instead???

It's possible I COULD go with a little bigger tires which makes me lean toward the 4.56's. No way would I go smaller again.

I just never see anyone with 3.73's recommended to run 3.90's or really even 4.11's when they run bigger tires. It always seems like everyone wants to jump to 4.30' - that's like 3 gear sizes (Obviously the size of the tires could have a huge bearing).

According to calcs and confirmed with the charts, 4.30's put me in the same sweet spot I had with 4.11's. I just don't want to do that and WISH I had installed 4.56's. And 4.56's are much easier to find.

Anyone put on slightly larger tires that made this gear swap?

4.30's or 4.56's and why?

 

I'm confused as to why you want such high gears? Especially since your tires arent all that big. I'm running 305/70/16 and I have 3.73..

 

The op is running a 5.4 not a 7.3 diesel so gearing is a big deal. I went with 4.30 and am running 285/70/17 and its a good fit. If you are going any taller tire I would go with 4.56 your truck will be happier.

 

That may also have something to do with your 13mpg. The higher gears will help on the highway, but taking off from a stop, higher gears will make your truck work less, and you'll use less fuel. I know there are calculators to be found with google for your effective gearing with your new tires and gears you have vs. your stock tire size. You might be surprised by what your effective gearing is vs. stock.

 

oops. Missed the 5.4!
That 13mpg is a little out dated. My old city mpg was 11 and freeway was 14 at best. I now get 15 city an around 18 hwy. My exhaust backpressure sensor was clogged with soot.

But I will also look into gearing for my truck.

 

Here's a couple of calculators for the OP and Trey. Turns out with my 285/75/16s and my 3.73 gears, my effective gear ratio is 3.59.

Effective gear ratio calculator here.
Gear Design Equations Formulas Calculator Effective Gear Ratio

Tire size calculator here. So you can get your tire size calculated into inches or mm.
Tire Size Calculator - tire & wheel plus sizing

Good for giggles even if you aren't planning a gear swap. Which is something I would very much love to do when I've got the cheese to do it.

 

Thanks for the links. According to them, my effective gear ratio is 3.60...

Stock tire being 235/85/16 according to the site
Current tire being 305/70/16
Current gears 3.73

 

There are also those and other calculators on this site:

Automotive Calculators offer to you by Ford Trucks Enthusiasts | www.ford-trucks.com

 

I forgot about the calculators. I was using the charts. Yes, I am effectively a 3.96 Ok, not bad, but I wanted the 4.11's when I got the truck.

If I plug in 4.30's into that calculator, my effective gearing changes 4.14 - right where I want to be.

I think that means I'll be looking for some deals on 4.30's gearing!! I have some other items I need to hit first but that should put everything back the way I wanted it.

Thanks guys!!

 

My advice is to go 4:56. Especially since you are towing. Although you didn't mention what you are towing, the common wisdom is that changing one gear step is not worth the cost. Add in the possibility that you will go larger tires, this is a no brainer. 4:56 gets my vote.

 

Truck spends majority of time as a daily driver. However, I do haul a 24' enclosed trailer with quads, gear, etc.

I thought the same thing about the cost vs. 1 gear change. But thought that 4.56 might be too tall (you know, I don't want to ruin my 24mpg I'm getting - hahahaha).

I don't know for sure that I'll go with bigger tires but I know I won't go smaller.
The truck never would light up the tires even with the 265's but the 285's made it worse. It's more that you can tell the shift points are not quite right. They need to be a little higher up in the RPM range.

I have an email in to Mike @ 5star about changing the shift points... But tuning does not replace a gear change.

 

I recommend 4.56.
One step to compensate for the larger tire diameter.
A second step to compensate for the HEAVIER tire.
That should get you closer to original performance feel.

The difference in freeway fuel economy will be negligable.

 

My 2005 F350 has the 5.4L 3V engine, 33" tall tires, and 4.10 gears. I wish that it had 4.30 gears. If I were to increase the tire size, I would recommend the following:

33" Tires - 4.30 Gears
35" Tires - 4.56 Gears (minimum)
37" Tires - 4.88 Gears (minimum)
40" Tires - 5.13 Gears (minimum), 5.38 Gears (preferred)

In my time at FTE, I have never heard of anyone wanting less gears but I have heard many wanting more gears. Best success!

 

Awesome! Thanks, I didn't know about that. I just used google to find the ones I posted.