Hi, with a powerstroke 7.3 diesel running 37" tires, what gear ratio is better?

Stock 3.7 or 4.56 gears?

What kind of milage could i expect city and highway?

And what will the rpm be turning at 70-75 mph?

thanks

 

https://www.ford-trucks.com/calculat...php/p-mph_rpm/

 

Thanks for the reply, i did the calculator, and it said at 70mph, 2200rpms, and 37" tires that the gear ration should be 3.4 Does that sound right?

Guy i talked to that is selling a truck with 37's and 456 gears said he gets about 16-18 mph on the highway with no load. And about 15 mph in the city.

Do you think that is BS?

 

No it is not BS.
You have to find the sweet spot between too high and too low of an rpm depending on how loaded the engine is going to be most of the time.
Going to be running empty, or at most with a bed full of equipement covered over with a canopy? I would go with 4.10's
Need to tow? Tow heavy? Then gear it lower. But I wouldn't tow with tires that big, you have to take into consideration that the brakes are now working that much harder to stop the truck too.
Your final decision on what gear ratio to use completly depends on what you plan on using the truck for.

 

those calculators definitely don't work right... they say that with my tire size and rpm i'm running 3.48 gears?!?!? i'm running 4.10s lol

 

I don't think that calculator considered the trans overdrive
if you know revs per mile of tire it is pretty easy to figure out

 

yeah i think that's using a 1.0 trans gear ratio.... i'll have to drive around with overdrive off and see if it's right

 

if I done the math right on the 3.48 and add the 29% overdrive it would come out to 4.49

 

humm maybe i had the rpms and mph off by a little... i guess 1 or 2 mph and about 100 rpms would make a pretty big difference

 

here is a calculator that works bettter
http://www.xse.com/leres/bin/gearrat...ference=116.24

 

humm are those gear ratios the same as the OBS? cause that's what i got lol

 

best gear calc out there.

http://www.grimmjeeper.com/gears.html

focused on 4x4's but at the bottom it works for street.

 

what is the transfer case and underdrive for our trucks with that www.grimmjeeper.com webstie?

 

since they dont list the 271 or the 273 i just put in the nvg241. it has the same ratios as the one in our trucks.
and for the underdrive, just leave that blank unless you have a klune, or blackbox.

 

so the reason to get a 4.10 or 4.56 would be for acceleration while your top speed decrease?