I've been scouring the forums for the information I'm looking for but I just don't seem to find the correct information. My 015 SD is geared from the factory with 4:30's but I'm not even close to my max weight rating of the truck @35k. I scaled at 26500 fully loaded with my 5er and was thinking of going down to 3:73's since that is the where the carrier break is. Has anyone done this and noticed any difference in how the truck pulls or behaves? I know the cost is a bit on the high side since I have to do both f&r axles. Only reason I want to do now is I don't tow as much as originally intended and have a Max load of2k lbs of tools anyway. And when i do pull a smaller trailer it's only weight is around 5-k
thoughts anyone?

 

How much fuel can you buy for the cost of the gear change verses how long it will take at the current MPG to use the equivalent $$ in fuel. Convert the miles in to years to cover that many miles.

I doubt your fuel mileage will increase drastically doing a gear change. So, if you gain 15% better mileage, how long in months and miles will it take to offset the cost of the gear change?

 

I roughly calculated my average fuel costs $4600/yr. So even if it was a rough15% savings it be $685/yr. The cost of the swap would be 2800 for both axles. So if the math is right it be 4 years to pay for it's self. Which is quite a bit of time.

 

Resale value is better with the 4.30 gears.
And you may not be satisfied with the performance of it with 3.73s.
It is extremely rare for anyone to want to go with taller gears, virtually everyone talks about going lower, id est higher gear ratio #.

 

I would love to have those 4:30s. my v10 truck with 3:73s and a 4500# 5th wheel isn't a dog, but some of those long steep pulls I sure wish I had more grunt. I get 9 mpg towing, and I bet id get 9 with the deeper gears too, but id be smiling all the way up the hill.

 

I swapped to 4.10 in my truck but I had 4.88 to begin with and it is 2wd. I wasn't also putting in a locker so the gear change was a second thought.

 

My guess is that even with just 2k in the truck, you will not gain any mileage dropping gear ratio’s. But if it is something that you think you truly want to do, it shouldn’t cost you a dime. There are countless people on this board that would love to swap you their 3.73s for your 4.30s. I think you would regret it though. What kind of mileage are you getting in what conditions?

 

I just went from 3.73 to 4.30. Towing my 9000k camper really made the truck work the skinny pedal and was getting ~7-8 mpg. After gear swap, different truck. I tow at 65-70 mph and mpg's improved to 9-10 towing and the truck does it soo much easier. I did not notice a drop in mpg's empty either. Though I do not drive it daily and I have no interstate commute.

As said it is your decision, but if you are asking for advice on what to do, DON'T! 4.30 gears are much more desirable in the gassers.

 

You MIGHT be the First to Want 3.73 and TOW anything..

find a fellow owner with 4x4 and 3.73 and exchange axles... no gear setup..

just R&R differentials.. and bleed brakes.
I bet you will have NO problem finding fellow "F" owners willing to do this.

I have 2 wheel drive.. and tow 9,000 pound trailer and would like 4.30's.
I tow twice a year. and truck is daily driver..

SECOND IDEA... just ADD larger wheels and tires.. problem solved..

 

OP- is your truck gas or diesel?

 

I would swap axles with you, and pay for the swap entirely if you were nearby. Shouldn't have a hard time finding someone near you to do the same

 

Is the truck Diesel or Gas? If its a gas truck then I would keep the 4.30s, if diesel then a 3.73 swap would give it better fuel mileage and it could still tow fine.

 

Tire height makes a big difference in gear selection.
I swapped from 4.88's to 3.73's and love them, but my tires are only 32" tall and my engine operates at a lower rpm.

 

Have you looked into installing a Gear Vendor overdrive unit?