I will be changing tires to a 33 or a 35. My question is will I need to change gears? On my window sticker is states " 3.73 RATIO LIMITED SLIP AXLE".

 

with 35" i would highly recomend a gear change to 4.56, or if you want alittle more low end 4.88

 

when i go 35s im only going to 3.73s. ofcourse i have 3.55s turning my 33s now. it all depends on what you do.

if you have the 5.4 then you will be able to turn 35s with stock gear but your not going to have as much "pick-up" as you did before. if you run mainly on street and you want the best gas mileage then go ahead and compensate with a taller gear. i think youd be good with 4.10s though.

 

Do you NEED to change gears, no. I have 3.73's with 35's and its not bad at all. I have mods though (Xcal2, exhaust and CAI) that probably offset it a little bit. I will someday switch to 4.56's (just because) but it's not anything i'm going to do real soon.

 

Just because?

 

with 35" and 3.55 your tranny is not in the RPM range it was designed for causing wear to your tranny, i highly recomend 4.56 with 35" to get your tranny back in the correct RPM range

 

heres the facts from stock 30in tires on 3.55 gears the correct power band for 35in tires is 4.10 gears also does not require a speedo recalibration however 4.56 compensates for the added weight of tire 4.88 for very low crawl ratios (and is best gas economy for normal citydriving) engine rpms a bit to high for highway economy for highway suffers 4.10's best highway gear (best fuel economy) 4.56 nice medium this all based for the 35in tire

 

I will be recieving my Superchips FlashPaq on the 2nd of Jan. With that said will that affect the choices for the gears?

I am now torn between the 4.10 and 4.56 gears. What do the gears run ($) for, and an average cost to have 'em installed?

 

you can adjust ur shifts making them more soild still no but it does help when in dought go higher 4.56's is a great choice for 35's but speedo recabation is still needed but your programer will take care of that

 

I agree with bigtruck.

FWIW there are lots of us that run 4.10s with street-sized or stock tires, let alone taller off-road tires, where 4.56 or 4.88 are often called for.

Here's a thread...
https://www.f150online.com/forums/sh...d.php?t=266836
...nice gain, stock wheels, and he's got a Whipple.

Here's where my RPM are with street tires & 4.10s:
https://www.f150online.com/forums/sh...d.php?t=263323
I get nearly 14mpg highway, and I've got a Procharger supercharger.

This is just an opinion...but these are heavy trucks and need all the gear they can get. You will not get the same gain in torque multiplication with any other bolt-on. Not saying that you have to re-gear with taller tires, but I believe you're leaving a lot of performance on the table by using a too-tall (lower numerical) gearset.

If you are able, I suggest driving back-to-back in a truck with shorter gears vs. one with taller gears. Especially with taller tires, it's a huge difference in power, with minimal (if any) MPG penalty.