Multi-gear-ratio portal gear box

1. A portal gear box assembly effective to lift and change the gear ratio of a wheel of an off-road vehicle, the assembly comprising a housing, an input gear sub-assembly, an output gear sub-assembly, and an idler gear sub-assembly effective for linking the input gear to the output gear;

wherein the input gear sub-assembly comprises an input gear operably connected to a driven input shaft, the output gear sub-assembly comprises an output gear operably connected to an output shaft, and the idler gear sub-assembly comprises at least one idler gear adapted to transfer power from the input gear to the output gear and at least one removable adaptor effective for holding said idler gear(s) in either a first position or a second position different from its first position; wherein the housing includes an input gear indent adapted to receive the input gear sub-assembly and to hold it in a first input gear assembly position within the housing, an output gear indent adapted to receive the output gear sub-assembly and to hold it in a first output gear assembly position within the housing, and an idler gear indent adapted to receive the idler gear sub-assembly and to hold it in a first idler gear assembly position within the housing.

2. The gear box assembly of claim 1 wherein the gear box is a portal gear box for an all-terrain vehicle (ATV) or a utility task vehicle (UTV), the input gear is the input gear of the portal gear box, the output gear is the output gear of the portal gear box, and the idler gear is the idler gear of the portal gear box.

3. The gear box assembly of claim 1 wherein the idler gear sub-assembly comprises two or more idler gears adapted to transfer power from the input gear to the output gear and two or more removable adaptors effective for holding the idler gear in either a first position or a second position different from the first position.

4. A method for changing the gear ratio of a portal gear box for an all-terrain vehicle (ATV) or a utility task vehicle (UTV), the method comprising:

a) providing a portal gear box assembly effective to lift and change the gear ratio of a wheel of an off-road vehicle, the assembly comprising a housing, an input gear sub-assembly, an output gear sub-assembly, and an idler gear sub-assembly effective for linking the input gear to the output gear;

wherein the input gear sub-assembly comprises an input gear, the output gear sub-assembly comprises an output gear, and the idler gear sub-assembly comprises at least one idler gear and at least one removable adaptor effective for holding the idler gear in either a first position or a second position different from the first position;

b) installing a first of said at least one removable adaptor in its first position;

c) subsequently switching said first removable adaptor from its first position to its second position by removing the removable adaptor from its first position and subsequently installing that removable adaptor in a second position.

5. The method of claim 4 wherein one or more of the input gear sub-assembly, the output gear sub-assembly, and the idler gear sub-assembly comprises more than one gear, and the method additionally comprises installing a first gear in one of the sub-assemblies, and then subsequently changing the first gear for a second gear when said first of said at least one removable adaptor is switched from its first position to its second position.

6. The method of claim 5 wherein the idler gear sub-assembly comprises two or more idler gears adapted to transfer power from the input gear to the output gear and two or more of said at least one removable adaptors effective for holding the idler gear in either a first position or a second position different from the first position.