Here are some CAD models that I have found around the internet that are for general ride on toys or Power Wheels. I have not tested these, so I cannot confirm their accuracy unless otherwise stated.
Power Wheels Jeep Re-Tread Printables Link
Power Wheels Body GrabCAD Link
Power Wheels Gearbox “Visual” GrabCAD Link
Power Wheels Gearbox 1 “Functional” GrabCAD link
Power Wheels Gearbox 2 “Functional” GrabCAD Link
Power Wheels Wheel Adapter GrabCAD link (Rear Rubber traction is not legal in PWND)
Power Wheels Wheel Adapter 2 GrabCAD link
Power Wheels Wheel Adapter 3 Thingiverse link
Power Wheels Wheel Adapter 4 Printables Link
Power Wheels Wheel Adapter 5 Printables Link
Power Wheels Wheel Adapter 6 Printables Link (Part #74460-2249 Modified 17mm axle)
Power Wheels Wheel Adapter 7 Printables Link (Part #74460-2249 Stock)
Power Wheels Gearbox Output 1 Thingiverse link
Power Wheels Gearbox Output 2 Printables Link
Power Wheels Gear 1 18t/80t Printables Link
Power Wheels Gear 2 10t/55t Printables Link (24v 4wd jeep from Big Toys)
Power Wheels Gear 3 10t/38t Printables Link (24v Ride On)
Power Wheels Steering Wheel Printable Link