Ok, I've been doing some homework on figuring out what the pitch of the different gears are for the various 7R gearboxes. I've gone to this site: http://www.engineersedge.com/gear_formula.htm
. It list various formulas for determining a gears pitch. The relevant formula for us is this:Pitch = (Number of teeth + 2)/Outside Diameter
or more simply P = (N+2)/OD
I had my stock
19t motors out of a unibody Jeep so I measure the diameter with my micrometer and it was ~.672". So that would an equation of:
P = (19t +2)/.672 or P= 31.25
Now that is not exactly 32p, but pretty darn close.
To verify some more I checked the stock
16t motors on the Extreme Machine I just picked up. The pinion gear diameter was ~.577"
P = (16t + 2)/.577 or P = 31.2
Again, this is darn close to 32p and virtually matches the pitch on the Jeeps 19t pinion gear.
So with this information, let's do some math on what the pitch should be for the various gears.
13-14 7R GB.
Don't know. If someone has a vehicle with those pinion gear tooth counts, could you throw a micrometer on them?15-16-17 7R GB.
It is known that the 16t pinion IS
32p, correct? If that is the case than the ideal equation would be:
32p = (16t +2)/.5625"
So, the diameter of the pinion gear would have to be the same for the 15t, 16t, and 17t pinion gear, correct? As such, that would mean the equation for the 15t pinion gear pitch is:
P = (15t + 2)/.5625" or P= 30.22 or P = 30..... 15tooth, 30 pitch pinion gear
. (Maybe 31 pitch actually? In the real life micrometer reading I did on my 32p, 16t and 19t pinions, they both had to be rounded up about 3/4 pitch to get to 32p)
Now, 17t pinion gear.
P = (17t + 2)/.5625" or P = 33.78 or P = 34.....17 tooth, 34 pitch pinion gear18-19-20 7R GB
that the 19t pinion gear is 32 pitch for this GB, right? As such, the ideal equation would be:
32p = (19t + 2)/.65625"
So, for the 18t pinion gear:
P = (18t + 2)/.65625" or P = 30.47 or P = 30......18 tooth, 30 pitch pinion
(Again, 31 pitch maybe? Does this need to be rounded up like my real life pinion gears?)
20t pinion gear:
P = (20 + 2)/.65625" or P = 33.52 or P = 34......20 tooth, 34 pitch pinion21-22-23 7R GB
the 22t pinion gear is 32 pitch, right? So, the ideal equation would be:
32p = (22t + 2)/.75"
So, for the 21t pinion gear:
P = (21t + 2)/.75" or P = 30.67 or P = 31 pitch? .....21 tooth, 31 pitch gear
(is this supposed to be 30 pitch maybe?)
23t pinion gear:
P = (23t + 2)/.75" or P = 33.33 or P = 33........23 tooth, 33 pitch gear
(is this supposed to be rounded up to 34 pitch maybe?)
What does this mean?????
If the middle gear number (16t, 19t, and 22t pinions) are all 32 pitch, then it looks like the lower pinion number, 15t, 18, and 21t pinion gears would be either 30p or 31p. The higher pinion number, 17t, 20t, and 23t would be either 33p or 34p.EDIT:
After some more research this morning I have found that for applications like these brushed motors we use, you are only really dealing with 24p, 32p, and 48p gears. Outside of those pitches, good luck trying to find oddball pitches like the the "off gears" would require to fit those same gearboxes. Power Wheels may be able to get those pitches close to 32 made, but they are not made for the aftermarket like we would be looking for.
Like Taz and Hootie have been saying all along, just stick with the middle gear number at 32 pitch for the gearboxes.