Lynnmor wrote:
Ford uses the 3.31 with 18” wheels only.
The Idea that 3.31 will out pull the 3.55 when both have the same tire size is absolutely incorrect.
If you read and understand my explanation above you will see that a 3.31 with 18" wheels can certainly out pull 3.55 gears and 20" wheels. The scenario above would exist with about a 15000 lb trailer going up a 4% grade. The same sort of scenario would take place in third gear with a 15000 lb trailer on about a 6-7% grade.
So on a 7% grade the trucks will drop into 3rd gear with 15000 lb trailers in tow. The 3.31 geared truck would rev to 2900 rpm and be travelling 55 mph..... the 3.55 geared truck would be travelling 52 mph at 2900 rpm.