gear ratio stuff

[bling821]

Can somebody help me figure out what gear ratio to change too? I have the 3.73 and just put 35" tires on and, as expected, my gas mileage took a dump. I was thinking of 4.10 or 4.30. I just want to get the RPM back to 2000 at 70 MPH. I figure that would get the mileage close to before and I'd get the sluggishness out of it. Are there any good websites to check out? I'd like to try and get the gears changed before the weather gets warmer and I start towing the boat around again. Right now the truck feels like I've got the boat back there so no telling how it will tow with the stock gears. Any help would be great.

 

[Elk]

Try these.
Gear Calculator
RICHMOND Street Performance Calculator

 

[Chopper Boy]

Try 4lo.com it should help you alot!! Good luck with the Gears
chopper boy!

 

[orion_134]

To use the calcs I think you need to know the OD gear reduction.
Jesse

 

[dlonno]

With 35's, I wouldn't go lower than 4.10's. I have 4.30 with 37's and its just about perfect. I could of even gone with 4.10. Those gear calculators always recommend to big a ring gear. I had 4.56's on 35's on my last psd and it was way too high rpms on the freeway.
Dave

 

[keanoknick]

Keep in mind that a big factor in your mileage, is the additional rotating mass of the bigger wheels and tires. I've got 38" tires, with 3.73's and have no problem towing. Lower gears will help offset the tire size, and get you back closer to stock RPM on the highway, but you'll still get lower mileage due to the rotating mass, and from the truck being higher, as it is less aerodynamic and now creates more drag. I would not spend the money to regear for 35's I don't think you'll notice that big of a difference over all, maybe a little off the line improvement though. just my .02

 

[Buffs F-350]

I have 35s with 3.73s and I dont have any performance issues. The mpg around town went down a little but on the highway it went up a little. The last post explained it very well.