EditSlot Car Motor Gear Ratios
EditTypes of Aurora "factory" Pancake Chassis Gears.
We're generally covering Aurora here, however Johnny Lightning, Model Motoring Thunder-plus, Bauer & Faller each have a few interchangeable parts.
Compatible Crown Gears
15t crown gears for 9t pinions
T-jet stock
long boss
15t crown gears for 12t pinions
T-jet Hop-Up
short boss
15t crown gears for 14t pinions
T-jet Tuff Ones
long boss
15t crown gears for 14t pinions
A|FX stock
short boss
19t crown gears for 14t pinions
A|FX Super II
short boss
Compatible Cluster Pinion Gears
9 tooth pinion gears
(T-Jet stock)
12 tooth pinion gears
(T-Jet Hop Up)
14 tooth pinion gears
(Tuff Ones stock)
When installing the Crown Gear, try to get it as close to the Pinion Gear as possible without binding. If the Rear Axle has too much 'side-to-side' play, consider using a small washer or shim to aid in adjustment.
EditGeorge Warner
There is a gear you are missing: the Formula (Slimline) crown gear. This makes an excellent replacement for use with the 12-tooth hop-up gear. 12-tooth gears are now manufactured by Wizzard so they are abundant. However, Wizzard makes no matching crown gear. The good news is that you can still buy NOS Formula (Slimline) crown gears. Web store ncphobbies.com has them. Part number: AUR8622fS.
I made some measurements on a bunch of crown gears. Specifically, I was looking at the width of the collar between the flat side of the gear and the end of the gear. Here is what I found:
Summary on collar sizes
-------
Hop Up Gear: 0.040" or 0.060"
Formula Gear: 0.060"
Stock Gear: 0.080"
Tuff Ones/AFX Gear: 0.030" or 0.035"
Super II Gear: 0.040"
~ George Warner