[starscream]

Papa, the gmaxx single speed locks the tranny in second gear. It doesn't effect the gear reduction so it remains the same 17.9 to 1.

Multiplication occurs when a gear is added to the same axis point such as the emaxx input shaft. This shaft shares the 66t spur and the 13/18t input gears. Since gears such as the idler gears do not introduce additional gearing on the same axis they do not effect the final gear ratio.

Here's how to calculate the stock emaxx gear ratio:
Lets take second gear for example.
We have the following gears
18t pinion
66t spur
**Change occurs so Multiply current ratio by the next ratio**
18t input
20t idler (doesn't introduce new gearing so doesn't really count)
31t output
**Change occurs so Multiply current ratio by the next ratio**
13t diff pinion
37t diff spur

66/18=3.67
Current ratio is 3.67 to 1

the 66t spur gear shares the axis with the two speed gears (2nd being 18t) so this is where a multiplication occurs after we divide the following:
31/18=1.72

3.67*1.72=6.31
current ratio is 6.31 to 1 next reduction...

The outputgear shares the same axis as the 13t diff pinion.
The f/r diffs have the following ratio
37/13=2.85

2.85*6.31=17.9

So the final ratio 17.9 to 1

You must also factor in the circumference of the tires to get the actual output to the ground shown in the previous example.

You should be able to figure out any gearing scenerio this way.

Sorry for the book but I thought it would be helpful.