Finally Caved
FTE Leadership Emeritus
Joined: Jul 2002
Posts: 42,561
Likes: 421
From: Long Island USA
Thanks for your input. Yes, I am still very confused and have even gone so far as to start considering trading up to an F350. I have gotten a lot of varying feedback with regards to the gearing change. My question is, in the end, is there a noticeable difference between the 3.73 you had and the 4.10 you have now?
Take any RPM and multiple by 1.1, the answer is what you'll be running at the same speed.
4.30 divided by 3.73 is 1.15, that's a 15% increase overall.
Thread Starter
|
FTE Leadership Emeritus
Joined: Sep 2003
Posts: 12,241
Likes: 755
From: Houston, Texas
There are actually two ways of figuring it out, I did it one way, Art did it the other...
There is a noticable difference as my truck more easily gets up, goes, and maintains speed better without much effort. The gears have done a great job of getting my truck and 35s moving down the road better.
There is a noticable difference as my truck more easily gets up, goes, and maintains speed better without much effort. The gears have done a great job of getting my truck and 35s moving down the road better.
Posting Guru
Joined: Feb 2015
Posts: 1,092
Likes: 0
There are actually two ways of figuring it out, I did it one way, Art did it the other...
There is a noticable difference as my truck more easily gets up, goes, and maintains speed better without much effort. The gears have done a great job of getting my truck and 35s moving down the road better.
There is a noticable difference as my truck more easily gets up, goes, and maintains speed better without much effort. The gears have done a great job of getting my truck and 35s moving down the road better.
Bringing this one back....
Are you still happy with the 4.10's and do you tow much and if so what kind of weight?
Thread Starter
|
FTE Leadership Emeritus
Joined: Sep 2003
Posts: 12,241
Likes: 755
From: Houston, Texas
On the highway he gets anywhere from 17-19 mpg and can tow like there's no tomorrow.
The transmission now has almost 300K on it and (knock on wood) not a single issue with it. All I've done is change the fluid.
The rear diff is still in good shape as well. Although I plan on putting in a Limited slip since Ford gave me an open diff on Rudolph...
My goal was to make Rudolph into a better Tow Monster than Ford originally designed him to be. Between the lift, gears, tires, and sway bars, I've accomplished that.
Posting Guru
Joined: Feb 2015
Posts: 1,092
Likes: 0
Before I start another thread, I can't understand how the 4.30 didn't work, your tire size grew by over 15%, therefore the gear ratio going up 15% is almost dead on to 4.30's
I have an 05 6.0, 3.73's and went to 305 70 18 cooper tires, 35.08 spec height.
Absolutely murdered my mileage across all boards, city, highway, towing, empty etc, 3mpg lost, that is hand calculated.
What I don't understand is if these trucks w diesels came with 4.10 with stock 265's and they jumped to 35's theyd be wanting to gear lower as well. - puttint them to 4.30 or 4.56 at least.
Currently I am at 1600-1650 rmp in OD w locked TC at 70mph. stock tires had me dead nuts at 2000 rpm.
If I go to 4.15 that is 10% difference, that puts it at 1815 at 70.
If I go to 4.30 that is 15% difference, that would put it at 1900 rpm at 70, sounds perfect.
If I tow and keep it at 60 it would be around 1628 rpm, again 5th gear locked TC, sounds reasonable
Currently I am at 1460 rpm at 55 mph!
The math doesn't lie, how does this not work?
To say the least, yes, I am confused.
I have an 05 6.0, 3.73's and went to 305 70 18 cooper tires, 35.08 spec height.
Absolutely murdered my mileage across all boards, city, highway, towing, empty etc, 3mpg lost, that is hand calculated.
What I don't understand is if these trucks w diesels came with 4.10 with stock 265's and they jumped to 35's theyd be wanting to gear lower as well. - puttint them to 4.30 or 4.56 at least.
Currently I am at 1600-1650 rmp in OD w locked TC at 70mph. stock tires had me dead nuts at 2000 rpm.
If I go to 4.15 that is 10% difference, that puts it at 1815 at 70.
If I go to 4.30 that is 15% difference, that would put it at 1900 rpm at 70, sounds perfect.
If I tow and keep it at 60 it would be around 1628 rpm, again 5th gear locked TC, sounds reasonable
Currently I am at 1460 rpm at 55 mph!
The math doesn't lie, how does this not work?
To say the least, yes, I am confused.
Thread Starter
|
FTE Leadership Emeritus
Joined: Sep 2003
Posts: 12,241
Likes: 755
From: Houston, Texas
As previously mentioned in the thread, 4.30 gears took the engine out of it's power band. I had great power around town, but on the freeway, I had little to no real passing power, even tuned.
I had the right answer the first time, but let everybody talk me out of it due to "rolling resistance" and other factors.
You can twist the math however, but is THE formula to use to calculate the correct gear ratio to the tire size:
New Tire Size/Old tire size x current gear ratio = Correct gear ratio to match current gear ratio with larger tires.
In the case of Rudolph:
34.6 / 31.6 x 3.73 = 4.08411392 or 4.10 gears
In your case:
35.08 / 33.2 x 3.73 = 3.94121686 or 3.92 gears
I geared my truck too numerically high and while it was probably better geared for constantly towing at 70 mph at 2200 rpms, it wasn't correctly geared for regular highway and city driving.
You also need to take into account that your speedo and odometer are now reading lower than what you're actually seeing. I'm sure that if you hook up your GPS, you'll notice that what your speedo and GPS say are two very different things. This is probably why it seems like you've lost mileage. Your PCM was configured for the 275/70/18 tires you more than likely had when your truck was stock. You PCM now needs to be configured for the larger tires you're running. Keep in mind the SCT only goes so far in configuring. You need an AE or IDS to do the rest. I recently went through this with The Monster and now have the speedo, odometer, and GPS agreeing on speed.
I had the right answer the first time, but let everybody talk me out of it due to "rolling resistance" and other factors.
You can twist the math however, but is THE formula to use to calculate the correct gear ratio to the tire size:
New Tire Size/Old tire size x current gear ratio = Correct gear ratio to match current gear ratio with larger tires.
In the case of Rudolph:
34.6 / 31.6 x 3.73 = 4.08411392 or 4.10 gears
In your case:
35.08 / 33.2 x 3.73 = 3.94121686 or 3.92 gears
I geared my truck too numerically high and while it was probably better geared for constantly towing at 70 mph at 2200 rpms, it wasn't correctly geared for regular highway and city driving.
You also need to take into account that your speedo and odometer are now reading lower than what you're actually seeing. I'm sure that if you hook up your GPS, you'll notice that what your speedo and GPS say are two very different things. This is probably why it seems like you've lost mileage. Your PCM was configured for the 275/70/18 tires you more than likely had when your truck was stock. You PCM now needs to be configured for the larger tires you're running. Keep in mind the SCT only goes so far in configuring. You need an AE or IDS to do the rest. I recently went through this with The Monster and now have the speedo, odometer, and GPS agreeing on speed.
Posting Guru
Joined: Feb 2015
Posts: 1,092
Likes: 0
As previously mentioned in the thread, 4.30 gears took the engine out of it's power band. I had great power around town, but on the freeway, I had little to no real passing power, even tuned.
I had the right answer the first time, but let everybody talk me out of it due to "rolling resistance" and other factors.
You can twist the math however, but is THE formula to use to calculate the correct gear ratio to the tire size:
New Tire Size/Old tire size x current gear ratio = Correct gear ratio to match current gear ratio with larger tires.
In the case of Rudolph:
34.6 / 31.6 x 3.73 = 4.08411392 or 4.10 gears
In your case:
35.08 / 33.2 x 3.73 = 3.94121686 or 3.92 gears
35.08 / 31.6 x 3.73 = 4.14 I guess I'd be about 1% higher geared than a stock EX with the 4.10's, probabaly splitting hairs taking the "Rolling Resistance" part out.
My stock tires were 265 75 16 when new so I am basing the percentiges of that
I geared my truck too numerically high and while it was probably better geared for constantly towing at 70 mph at 2200 rpms, it wasn't correctly geared for regular highway and city driving.
Can you give me the RPM you run currently at 70?
You also need to take into account that your speedo and odometer are now reading lower than what you're actually seeing. I'm sure that if you hook up your GPS, you'll notice that what your speedo and GPS say are two very different things.
My Edge internally tracks the correct drive miles after putting in the correct tire size, OEM odometer is innacurate at this point. My speeds / RPM are based on using a GPS on flat ground for half mile at a time to remove any variances, again TC locked in fifth.
This is probably why it seems like you've lost mileage. Your PCM was configured for the 275/70/18 tires you more than likely had when your truck was stock.
My PCM is set for the 265/75/16's
You PCM now needs to be configured for the larger tires you're running. Keep in mind the SCT only goes so far in configuring. You need an AE or IDS to do the rest. I recently went through this with The Monster and now have the speedo, odometer, and GPS agreeing on speed.
I had the right answer the first time, but let everybody talk me out of it due to "rolling resistance" and other factors.
You can twist the math however, but is THE formula to use to calculate the correct gear ratio to the tire size:
New Tire Size/Old tire size x current gear ratio = Correct gear ratio to match current gear ratio with larger tires.
In the case of Rudolph:
34.6 / 31.6 x 3.73 = 4.08411392 or 4.10 gears
In your case:
35.08 / 33.2 x 3.73 = 3.94121686 or 3.92 gears
35.08 / 31.6 x 3.73 = 4.14 I guess I'd be about 1% higher geared than a stock EX with the 4.10's, probabaly splitting hairs taking the "Rolling Resistance" part out.
My stock tires were 265 75 16 when new so I am basing the percentiges of that
I geared my truck too numerically high and while it was probably better geared for constantly towing at 70 mph at 2200 rpms, it wasn't correctly geared for regular highway and city driving.
Can you give me the RPM you run currently at 70?
You also need to take into account that your speedo and odometer are now reading lower than what you're actually seeing. I'm sure that if you hook up your GPS, you'll notice that what your speedo and GPS say are two very different things.
My Edge internally tracks the correct drive miles after putting in the correct tire size, OEM odometer is innacurate at this point. My speeds / RPM are based on using a GPS on flat ground for half mile at a time to remove any variances, again TC locked in fifth.
This is probably why it seems like you've lost mileage. Your PCM was configured for the 275/70/18 tires you more than likely had when your truck was stock.
My PCM is set for the 265/75/16's
You PCM now needs to be configured for the larger tires you're running. Keep in mind the SCT only goes so far in configuring. You need an AE or IDS to do the rest. I recently went through this with The Monster and now have the speedo, odometer, and GPS agreeing on speed.
To be clear, I am not discounting anything you did or changed, clearly you have the first hand experience and that as why I am looking at your set up for answers, just trying to understand it better.
Joe
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
AEV FXL Super Duty - the Super Duty Raptor Ford Doesn't Make
Brett Foote
Lobo Vs Lobo: Proof the F-150 Lobo Should Be Even Lower!
Michael S. Palmer
Ford's 2001 Explorer Sportsman Concept Looks For a New Home
Verdad Gallardo
10 Best Ford Truck Engines We Miss the Most!
Joe Kucinski
2026 Shelby F-150 Off-Road: Better Than a Raptor R?
Brett Foote
2027 Super Duty Carhartt Package First Look: 12 Things You NEED to Know!
Michael S. Palmer
10 Most Surprising 2026 Ford Truck Features!
Joe Kucinski
Top 10 Ford Trucks Coming to Mecum Indy 2026
Brett Foote
5 Best / 5 Worst Ford Truck Wheels of All Time
Joe Kucinski
Super Moderator
Joined: May 2004
Posts: 29,380
Likes: 118
From: Central Coast of CA
If you have AE, you can adjust your speedo so it'll be accurate with the 35's.
Stewart
Posting Guru
Joined: Feb 2015
Posts: 1,092
Likes: 0
Edge CTS, programmer is set for correct tire size, odometer is not.
My calcs and readings are based on using GPS and actual miles logged etc.
When you say you run higher RPM are you stock geared and are you running higher at true 70 MPH?
Thread Starter
|
FTE Leadership Emeritus
Joined: Sep 2003
Posts: 12,241
Likes: 755
From: Houston, Texas
35.08 / 31.6 x 3.73 = 4.14 I guess I'd be about 1% higher geared than a stock EX with the 4.10's, probably splitting hairs taking the "Rolling Resistance" part out.
Correct....
Can you give me the RPM you run currently at 70?
Approximately 2000 rpms
My Edge internally tracks the correct drive miles after putting in the correct tire size, OEM odometer is innacurate at this point. My speeds / RPM are based on using a GPS on flat ground for half mile at a time to remove any variances, again TC locked in fifth.
You need an AE or IDS to correct this. I've tested this on my truck and between setting my SCT for the proper revs per mile and telling the PCM I have 33 inch tires, my speedo and odometer are dead on.
If I had to guess, the previous owner did you a solid and put in 4.30 gears instead of leaving them stock or putting in 4.10.
Correct....
Can you give me the RPM you run currently at 70?
Approximately 2000 rpms
My Edge internally tracks the correct drive miles after putting in the correct tire size, OEM odometer is innacurate at this point. My speeds / RPM are based on using a GPS on flat ground for half mile at a time to remove any variances, again TC locked in fifth.
You need an AE or IDS to correct this. I've tested this on my truck and between setting my SCT for the proper revs per mile and telling the PCM I have 33 inch tires, my speedo and odometer are dead on.
If I had to guess, the previous owner did you a solid and put in 4.30 gears instead of leaving them stock or putting in 4.10.