Hey i have an 02 f350 with 37 inch tires and am getting a new trailer about 7800 lbs empty and about 10,000-12,000 lbs loaded. So i want to get gears, and still be able to cruise doing 60-70mph without it screaming. i currently have 3.73 and sometimes already going up hills pulling my current 3 horse trailer about 6500 pounds loaded third gear can be sluggish.

I have the 6 speed manual so im thinking either 4:10, 4:30, or 4:56, and just maybe 5:13 but i think that will be to low.

My truck is my daily driver and i tow a couple times a week, and in the furture will probably be making couple hundred mile plus trips over passes with and without my new trailer.

So what gears do you think i should get and what do the rpms like like at 60 and 70 mph.

Thanks
Michael

 

4.30's is what I run on 36" tires. Personally I think it's perfect, and RPM's on the highway are almost like a bone stock truck. Tows like a beast too.

 

whats the rpms doing 60? and the 70V

Thanks
Michael

 

My truck, 325/60r20's (35.5") and 4.30 gears:

60 MPH = 1750 RPM's
70 MPH = 2050 RPM's

That's pretty darn close to what it would be if it had stock 265/75r16's (31.65") and stock 3.73 gears. In stock form:

60 MPH = 1700 RPM's
70 MPH = 2000 RPM's

Now here are some comparisons for your truck running 37's. These are rounded to the nearest 25 RPM's, so they aren't exact but should give you a very good idea of where you'll be.

3.73's
60 MPH = 1425 RPM's
70 MPH = 1725 RPM's

4.10's
60 MPH = 1600 RPM's
70 MPH = 1900 RPM's

4.30's
60 MPH = 1675 RPM's
70 MPH = 1975 RPM's

4.56's
60 MPH = 1800 RPM's
70 MPH = 2100 RPM's

Hope this helps.