Stage 1: The Differentials

The output shafts of the differentials come pre-assembled. Check that the gear on the output shaft is true i.e. not wonky. It is difficult to tell with such small parts. I only found out after completing stage 1 and 2 and feeling that the completed diff and gearbox did not operate smoothly. One way of getting an idea if the assembly is not true is to put the shaft in a power drill and spin it up and see if it looks ok or not. When assembling the differentials the instructions say to apply a liberal coating of grease to the gears. It would also be beneficial to grease or oil the washers that go between the output gears and the main drive gear and differential cover and the output gears shafts.