Question 3.73 vs 3.55

[Rusty74]

I have also ran these Ford trucks with verious gear selections and 3.55 would not work in a gas truck pulling grades. I checked into this with some 4x4 shops in town before I bought mine. The general sensus is these trucks make so much power it would only be noticeable from a start. I agree with all the responces, but why would Ford put 3.55 in a F-350 with 18" wheels and 3.73 with 20" wheels? Due they equal the same ratio?

 

[yukondiesel]

I have also ran these Ford trucks with verious gear selections and 3.55 would not work in a gas truck pulling grades. I checked into this with some 4x4 shops in town before I bought mine. The general sensus is these trucks make so much power it would only be noticeable from a start. I agree with all the responces, but why would Ford put 3.55 in a F-350 with 18" wheels and 3.73 with 20" wheels? Due they equal the same ratio?

If you get the tire specs in revolutions per mile, that being the REAL final drive ratio, compare the revs per mile of each tilre size, calculate the percentage diffference, then calculate the percentage difference between the 3.55 and the 3.73, I think you find that yes, the 3.55 with the 18 inch tires (from Ford) and the 3.73 with the 20 inch tires are nearly the same. Its not as complicated as it sounds...try it

 

[Rusty74]

I did some quick math and came up with 3% diffrence on the tire (Rotated 3% less w/ 20") and 5% diffrence on the gear raito (5% Less w/ 3.55). So there is only a 2% total diffrence between the gear selections from Ford? (Stock tire selections were used to calc) Let me know if I'm wrong, it's late.

 

[yukondiesel]

I did some quick math and came up with 3% diffrence on the tire (Rotated 3% less w/ 20") and 5% diffrence on the gear raito (5% Less w/ 3.55). So there is only a 2% total diffrence between the gear selections from Ford? (Stock tire selections were used to calc) Let me know if I'm wrong, it's late.

Yup...sounds about right to me Thanks and regards..Joe

 

[hntnv]

Well I ended up with the an 08 that had the 3.55's. It only has 180 miles but I couldn't wait to pull the trailer. I pulled it about fifteen miles just to see how it does and I don't have any complaints. The truck pulled awesome. One thing I notice from this discussion is that most of the 3.55's came with 18" rims. While the 3.73's come with 20". My truck has the 3.55's and has 17" rims that come with the chrome package. Truck is great. Thanks for all the info..