Biggest tires with the Non-Sas 3.73?

[Bruno]

What are the biggest tires I can use with the Non-Sas 3.73?
Im concerned if I go to a 35" it will start to effect drivability + many other things.
Is there some sort of chart, that has recomended ratio to tire size?

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[Bruno]

Or are we supposed to change the Ring & Pinion when changing tire size?
For example 35"s on a 3.73 Ratio looks like I need to do a 2328 Ring & Pinion?
Thanks I am sure many people on here know all about this stuff & I am totally uneducated on this subject.

https://www.4wheelparts.com/the-dirt/a-guide-to-gearing/

 

[2020FordRaptor]

Or are we supposed to change the Ring & Pinion when changing tire size?
For example 35"s on a 3.73 Ratio looks like I need to do a 2328 Ring & Pinion?
Thanks I am sure many people on here know all about this stuff & I am totally uneducated on this subject.

https://www.4wheelparts.com/the-dirt/a-guide-to-gearing/

That's more if you're engine can't handle the extra weight and resistance of 35s. You should be fine not changing the rear gears.

 

[BigGarnet]

Or are we supposed to change the Ring & Pinion when changing tire size?
For example 35"s on a 3.73 Ratio looks like I need to do a 2328 Ring & Pinion?
Thanks I am sure many people on here know all about this stuff & I am totally uneducated on this subject.

https://www.4wheelparts.com/the-dirt/a-guide-to-gearing/

I wouldn't use that chart...it only takes 1/3rd of the gearing into account. Use a calculator in which you can put in all the factors and compare. Like this one:

http://www.grimmjeeper.com/gears.html

I wouldn't want to run 35s without re-gearing, but a lot of people think it's fine.

 

[peterh]

I have read some on here say no power loss with non-Sas and 285/75/17s.

 

[IDyeti]

For example 35"s on a 3.73 Ratio looks like I need to do a 2328 Ring & Pinion?

That's not ring and pinon size, that's RPM of engine at a set speed.

I wouldn't run more than 33's on 3.73s, just personal experience with other rigs.

 

[Bruno]

That's not ring and pinon size, that's RPM of engine at a set speed.

I wouldn't run more than 33's on 3.73s, just personal experience with other rigs.

Oh, yea, boy I feel really stupid now

 

[kodiakisland]

Or are we supposed to change the Ring & Pinion when changing tire size?
For example 35"s on a 3.73 Ratio looks like I need to do a 2328 Ring & Pinion?
Thanks I am sure many people on here know all about this stuff & I am totally uneducated on this subject.

https://www.4wheelparts.com/the-dirt/a-guide-to-gearing/

These charts are from the old days that most here don’t even remember but the charts live on. These charts are for final drive ratio of 1:1, and it’s been a long time since overdrives became common. Doesn’t take into account first gear at all, which for me is the most important.

Use an actual calculator that uses your transmission gears to accurately gage what is acceptable to you.

 

[dbattle]

Anyone have experience with 305/70 R17 on a 3.73? Approximately 33.8".

 

[Bradley Thornton]

This one is closer to real numbers. Now size tire I would say 35in as my guess. To be fair thats an educated guess being I added 37 on a stock Sasquatch.

 

[mpeugeot]

Anyone have experience with 305/70 R17 on a 3.73? Approximately 33.8".

2.3 or 2.7?

First, my personal experience is with 33.5" tires and 4.27 gears on a 2.7 2 door Bronco with an approximate curb weight of 4600#. There is no shortage of power and in 4 low, with sticky enough tires, it would probably be able to crawl vertical walls with the Advanced 4x4 transfer case. The 10 speed transmission is a great asset in running larger tires than would be otherwise advised and the low-end torque of the ecoboost engines are also a significant factor in being able to run even 35's with a 2.3 liter using a 3.73 differential. It isn't optimal, but unless you are hard core off-roading, you will be just fine!

What you will effect with larger, heavier tires is fuel economy. You will pay a price at 75 MPH with regard to the MPG. 35's and 37's are about 1.5-2x the weight of a light A/T tire used on the OBX. This typically is a 15-25% penalty in MPG depending on many factors. I can get as high as 23.5 MPG with the stock OBX tires and a free flow exhaust. Put the factory exhaust in place and my 33.5" mud-terrain tires back on and my fuel economy dips to 18 MPG or so. That's a 25-30% change in fuel economy!

 

[dbattle]

2.3 or 2.7?

First, my personal experience is with 33.5" tires and 4.27 gears on a 2.7 2 door Bronco with an approximate curb weight of 4600#. There is no shortage of power and in 4 low, with sticky enough tires, it would probably be able to crawl vertical walls with the Advanced 4x4 transfer case. The 10 speed transmission is a great asset in running larger tires than would be otherwise advised and the low-end torque of the ecoboost engines are also a significant factor in being able to run even 35's with a 2.3 liter using a 3.73 differential. It isn't optimal, but unless you are hard core off-roading, you will be just fine!

What you will effect with larger, heavier tires is fuel economy. You will pay a price at 75 MPH with regard to the MPG. 35's and 37's are about 1.5-2x the weight of a light A/T tire used on the OBX. This typically is a 15-25% penalty in MPG depending on many factors. I can get as high as 23.5 MPG with the stock OBX tires and a free flow exhaust. Put the factory exhaust in place and my 33.5" mud-terrain tires back on and my fuel economy dips to 18 MPG or so. That's a 25-30% change in fuel economy!

Wow! Super helpful, thanks! My order is for a 2.3. I was considering upgrading to the 4.27 but I've just learned that I'll lose my price protection if I do that, so I'm less inclined if I can still run 305's. I don't do any hard core off-roading.

Again thanks, that was amazingly thorough and concise all that same time.

 

[kodiakisland]

This one is closer to real numbers. Now size tire I would say 35in as my guess. To be fair thats an educated guess being I added 37 on a stock Sasquatch.

Same chart, same numbers, different colors.
1:1 ratio isn’t what you should be looking at, unless you’re still rocking a power glide.
Both charts are for rpm at 65mph with a 1:1 ratio, which just doesn’t apply to todays transmissions.

Use the calculator on the above link for grimmjeeper to see what your rpms really are, since you do have 3 gears higher than 1:1.

 

[Dad life]

I drove a 4 door 2.3 base with 3.73s, auto, and aftermarket 35s. I was amazed that it wasn't bad at all. I wouldn't go any bigger than that, and I personally would choose very light wheels and decently light tires (the stock Goodyears are hard to beat in that regard). But it's certainly drivable thanks to the A10's gearing.

 

[kodiakisland]

Bottom line, 35s and 3.73 in the auto will be underpowered off the line, but more skinny pedal and turbo will make up for it. You’ll rarely use 10th gear, but the auto will select it for you anyway. If you need power off-road that’s what 4-lo will be for. Certainly not ideal but most will learn to live with it.

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