Jason660

Hey all. First post. Wondering what everyone thinks of the 3:73 gearing in their 5.0 power train? I'm running a 2013 Supercrew with a 5'5 box, 5.0 with 3:55 gearing. I'm wondering how much rpm difference there is when empty cruising.

BRUTE448

i think its about 2000 v 2150 rpms at 70 or so, but im uping to 275/70 or 295/70 in 18" when tires are due for replcment so ill be efftivly be aroud 3.55 //math is from 3.73 an oversize tires

Mike Up

3.73/3.55 = 1.0507

2000 rpms with 3.55 axle = 2101.4 rpms with 3.73 axle

daveak

I am a little under 2000 rpms at 70.....

Boulevard

The difference between the 2 gear sets is about 100 rpm in all gears, at all speeds. If you go to a hp/torque chart you will see that 100 rpm equals a change of about 10-15 hp. Basically, there is no difference.

Wannafbody

Stick with the 3.55 and put a slightly smaller diameter tire on it

Mike Up

The right tire size to equal a 3.73 gear using a 3.55 axle is 30.47" in diameter. Original tire diameter is 32.1" .

Scarlet

I'm at 1500 rpm at 55 mph, 1600 rpm at 60 mph, 1750-1800 at 65 mph. '11 Lariat 4x4 supercrew, 5.5 bed, 6.2, 3.73 LS rear. I've tried the smaller tire diameter on several cars in the past, one being my '94 T'bird 4.6. It was fine for a Friday or sat. night cruise, but I wouldn't do it on a daily driver again. Just looked funny, and the trans shifted odd.

Jason660

Wow. I thought there would be more difference from the 3:55's. It's saying I can haul more with the 3:73's, which was what I was focused on. I don't haul much at all but was investing in a pull type trailer this fall and was going to step up the gearing so it would pull a trailer better (20 - 25 ft trailer). I'm running the 20 inch Pirelli's, so not sure what that will equate to.

Boulevard

You are about to step into a whole **** storm of an argument with this and the bottom line is that there IS NO DIFFERENCE between the 3.55 and the 3.73 gear set other than the s**t that FORD is printing and I am pretty sure that my last post shows this. So as far as the trucks go, whatever you can pull with the 3.73 you can pull with the 3.55. That said, legally and by the numbers, the 3.73 equipped trucks are, by law, allowed to pull about 1700 lbs more than the 3.55's. No one that I know of is paying any attention to that last bit.


I have the 5.0 with the 3.55's and the 20's with the same scorpions that you have and I currently tow a 25 foot trailer in at 6000lbs without breaking a sweat. My next trailer is already picked out and it will come in at about 8500lbs loaded which is about 1000lbs over my listed capacity.


Some of the trucks with 20" wheels came with a heavy(er) than standard rear axle so check your door. It should say something like 4050lbs rear axle rating instead of the 3750lb axle.


The Scorpion tires on 20" rims tow a lot better than any 18" rim with any P rated tire. Trust me I have both the 20's and the 18's and the 18's are now only used in winter when I am not towing.