I have an 02 7700 with a 10.25 rear. It came from factory with 3.73 gears. I had it upgraded to 456 front and rear. I use it for mostly city driving but did a 360 mile round trip towing a 99 Navigator and it performed well. Gas mileage fell off a little but the performance was great. I run about 32.5 inch tires and am in process of running 34's in spring/summer.
For the cost I felt install a little lower gear to help with performance or if go to larger tires in future.

Rus

 

Just curious...what was your mileage on that 390 mile trip? Do you have a 5.4L? My tires are almost 34" tall so I am highly considering the 4.56 over the 4.10 since I'm going to be investing a lot in the upgrade. I just don't want my highway mileage to take too big of a hit. Right now my average mileage is about 12.5 mpg with 3.55s and I don't see how it would get worse than that with 4.56 gears. They will help the city and not be too much worse on the highway since I'm always shifting out of OD anyway with the 3.55's.

 

I have the 5.4 motor and my truck is at right about 12.5 on way out and about 11.5 on way back. This was doing about 70 mph both ways on cruise except for a 50 mile 45 mile treck through the mountainous Vermont country side both ways. I have the speedo calibrated to the tires/gears also so my numbers are accurate. This was on summer gas. We have a winter mix on gas in NY that reduces mileage also so no numbers on that yet.
My truck is stock except gears and the Hypertech 87 performance tune and has 67,000 miles now. With 456 never needed to shift out of OD. If you're shifting out of od in 3.55 it is basically same as a 4.30 in OD.

Rus

 

I made some RPM calculations in a spreadsheet and plotted them to try to help my decision. My truck as it came stock is shown in blue. My truck as it stands currently is shown in yellow. Option #1: 4.10 gears is shown in cyan. Option #2: 4.56 gears is shown in green. For reference I calculated the RPMs for a F150 with payload package (245/70/17 tires w/4.10 gears) and plotted it in red.

I'm still torn between the 4.10 and 4.56 for my upgrade. Since it will cost the same either way I'm tempted to go with the 4.56 and get more bang for my buck. I do drive I decent amount of highway though so I realize my mileage will suffer. If there are any other comments or advice after seeing this plot let me know. Thanks!

 

Should i go with 4.56 or 4.88 with 37's and anyone know of any packages that have both front and rear gears and master install kits as a package? someone said americantrucks.com did but I don't see anything

 

Not sure about the package thing but I would go with 4.88's for 37's. 4.56's are good for 35's but 4.88's would be better for something bigger like a 37.

 

imo go 4.56s i ran 4.30s with 35s on my bronco with a 302 and could barely hold od. i thought when i did gears id be screamin. always over gear. youll be very happy how your truck does loaded and unloaded. the mileage you lose on the freeway will be to a min and you will seriously save it in the city.
and for those who say oh no it wount hurt your trans. no a 33 over stock wont be to bad but step to a 35 and compare the same driver with a stock tire and the 35 and guarenteed the one with the 35s will have to be rebuilt first. in a previous post you said you wont go bigger than a 35. so at some point you may go a 35 and want the extra gear. anyone who has an idea on how a trans works will understand why. bigger tires cause the clutches to slip more producing 1. more heat and 2. more ware. will you be effected by it with 33s most likely no. but start towing with them on stock gears and yes your trans life will be decreased. trust me from experiance i know ive lost 2 different trans before i regeared and never had a problem after that.

 

This is same methology I would use. 4.56 35's 4.88 37's

 

I have the 4.10s in my truck (payload package). and your gearing chart is just right. When I went to a 33 inch OD tire, my equivalent ratio was about 3.85:1. Just perfect for this truck. I saw a slight mileage improvement over the 4.10s and the stock tires. That was a little surprising considering these are moderately aggressive tread tires (which normally eat up some mpg due to increased rolling resistance). My conclusion is that the engine liked the rpm drop.

My 70 mph rpm is about 2180, so my combo falls right into line with your 305/4.56 combo.

I will soon be trying a set of far less aggressive all season tires for winter use in the same size, so we'll see how much rolling resistance plays a part on my truck. I try to stay at or below 65. At 70, rolling resistance and the loss of aero from the winch bumper really starts to eat into mpg.

 

My local shop quoted me $1800 for the gear swap. That includes labor and parts. Does that sound reasonable for just the gear swap? I've always read around $1500 on here so I'm not sure if they are a little high or not.

They are looking into the rear differential price for me if I want that done too. I assume it is best to only upgrade the rear differential and leave the front open? How much additional should I expect for a true trac or Eaton posi in the rear? Thanks again for all of the info to help me get though this.

 

I had mine done for 1000 with me buying my own gear sets/bearings. Totalled 1600 as I had the rear seals and bearings changed also. I left the factory posi in rear and the fe open. 1800 good deal