On a RC car that has a 2 speed gear box, the larger gear wheel will have a one way bearing in the middle which assists the gearbox and spins in one direction by sitting on the gearbox but will not spin in the opposite direction.
If the air or area is cold and or dirty then you may find that the one way bearing could fail due to the great becoming cold or dirty so looses its liquidity meaning the bearing to slip. If this is the case then attempt to warm up the car and gearbox for 5 to 10 minutes by means of a small heater, hairdryer and you should find the problem goes away.
If the problem reoccurs then the first gear wheel will need to be removed and wd40 or similar applied to the bearing and shaft. Using the wd40 make sure the shaft and the centre of the one way bearing remove all grease. You can then apply fresh grease but making sure it is one way bearing grease. You will find that remove the RC cars gearbox is pretty easy but will take a little while.
To remote the gearbox, find the 4 screws underneath the chassis and remote them and then remote the screws which hold the top chassis on. The servo cable will be attached so you will not be able to remove the upper chassis but it can be moved out the way enough. You can then access the gearbox and put back in ok with enough clearway. To put the drive shafts back into the drive cups can be tedious but find some tools such as pliers to keep them out the way. Once you have cleaned the bearing, if it slips still then you may need to replace it.
Some other reasons why your rc car might not move such as -
If the brake pads are touching or to tight can cause It not to move. Also if the car has been through water and the brakes are wet they could of expanded which stops the breaks from disengaging. You will A grub screw could of come loose which is normally connected to the drive cups, this allows the drive cup to go round so stopping the drift shaft from turning and moving the car.
A part or parts inside the differentials could of snapped or not tight enough. This area means you will need to open up the differentials and give a visual inspection to see if anything looks wrong. Have a look at the cogs, maybe they are slipping or worn out. If they are worn then they should be replaced instead of trying to fix them up and move them together more. For more information on Petrol RC Cars then see or website.
Source: www.articledashboard.com
