It is easy to figure out yourself. Just put it in each gear and turn the input shaft counting each full revolution in order to make the output turn 1 revolution. The 1:1 gear set will be the gear which you need to turn the input 3 time in order to make the output turn 1.

I know this is an old post but I Stumbled across this in a google search. it was the impetus for me to do some work to try to understand how the ratios could be calculated and verified by counting rotations manually, so I felt like it might be worth resurrecting it.

Long story short, I took the tooth counts from the gears my transaxle and put it in all into a spreadsheet and did the math on it and for some reason it was not matching up to what i measured counting by hand. Turns out, that if you have an open diff (stock unit) and you haven't put a spool in it, or welded the gears, you will need to make adjustments to your rotation count. with one axle not spinning, the other will turn half the amount due to the 1:1 counter-rotations of the spider gears. So, if you are counting 6 rotations at the input shaft with one axle stationary with an open diff, it is actually 12:1 reduction. My 4150 5-speed ended up being as follows:

1st gear 50:1

2nd 33:1

3rd 20:1

4th 16.5:1

5th 12:1

Rev. 40:1

Where the higher number is the rotations of the input pulley and the second is one rotation of the ring gear.

All it really takes is looking at the parts diagram, and using the tooth counts and dividing all of the input gears by the output gears in terms of mesh.

an example of this would be:

(1st pinion # teeth*1st gear input # teeth*spur gear # teeth*comb gear min # teeth)/(bevel gear # teeth*1st gear driven*comb gear maj # teeth*final drive ring gear # teeth)

which for me was:

(14*12*14*12)/(42*37*35*32) = 28224/1740480 = 1/62

Or:

0.02 in decimal form

which is 1/50

Hence 50:1

None of the gears were anywhere close to 1:1

Which can be verified by turning both axles together and back driving the input shaft to count rotations, or assembling the unit and making the turns at the input shaft with both wheels on the ground going straight, or by holding one axle still (non locker) and doubling the counts at the input shaft that gives you one turn of the free axle.

working with ratios in decimal form was a bit of a mind bender for me so it took some getting used to. I can provide the spreadsheet and the diagram I used if anyone wants to take a look.

From this, I was able to calculate the speed etc...

Hope that helps!