I think I've read about every post on here abour regearing, but haven't come to a final conclusion. Most of the posts I see are regearing for larger tire size. I have a marginally larger tire. Stock was 30.05(255-65-17) and I swapped them for Lariat wheels, 30.52(265-60-18). The reason I want to do the gear swap is for towing. I currently have 3.55's since my truck did not come with the OEM tow package. BTW, it is a 2006 XLT 4.6l with an Edge tuner(no other mods). I am considering going to a 4.10 ratio for more torque. I'm not concerned about gas mileage, but want to know if I will still be able to cruise at highway speeds(65-80) comfortably. Would I be better off going to the 3.73's that came factory with the tow package? Thanks!

 

You can go to ringpinion.com and they have a calculator on there that will give you the right rpm for specific tire and gear combo's. With your current gear and tire size your only turning 1916 rpm at 70 mph. If you went with a 3.73 gear at 70 mph you would be turning 2013 and with a 4.10 gear you would be turning 2213 at 70 mph. I have an 01' Supercrew w/5.4L and 2wd. My tire height is 32" with a 4.10 gear and at 70 mph I'm turning roughly 2100 rpm. I love the difference in the take off power but when I pull my boat I have to slow down a bit because with overdrive turned off at 60 mph I'm turning 2650 rpm. Hope this helps with your decision.

 

While those gear/tire calculators are accurate, you tend to get inaccurate results using inflated tire diameters. The data that will give greater accuracy, is the manufacturer's revolution per mile data. Essentially both tires have a similar rev per mile for both tire sizes I looked up, being 691 and 685. That equates to a rolling diameter of ~29.55". Using that in the gear charts will give you more accurate results.

Here are the rpm at 70 mph for each ratio.
G/R 3rd gr 4th gr
3.55 2,836 1,980
3.73 2,980 2,080
4.10 3,276 2,286

Going 80 with the 4.10s will put you at 2,613 rpm, which isn't that bad. You didn't say how big your boat was, but if you are having to tow in 3rd now, I'm not sure you wouldn't still need to do that after the gear swap. I don't think there is enough of a difference between 3.55 and 3.73 to do that swap.

 

Don't go from 355 to 373. complete waste of $$. Go to 410's. My 05 w/tow package had a 355 from factory (4.6) Its a dog absolutely. No mods other than FM44, dumped in front of rear tire. 430's are an option also but there hard to find.

 

The 4.10 should be adequate.