Pay extra for the the upgraded version.
This is the cheaper version because of the plastic gearset, differential cups, and axle ends. The drive axles will break after a short time, and the replacements will do the same. The plastic gears will strip next, then the diffs, and evntually the scews that hold the wheels on will go and those turned out to be irreplaceable. We have two of these cars and both have the same issues. I've tried the "upgrade" all-metal driveshafts and many do not fit well and none worked with the stock diffs. You'll also have to convert it to pinlock axles when the screws break as they dont sell the screws. You need to upgrade the diffs and the driveshafts and find a combo of the two that doesn't bind during shock compression. (Metal ones are about 1mm longer than the plastic)
Also, the stock axles are way too tight in the wheel bearings. (See it sanded down in the picture)
Otherwise it's a great car. My kids love them. The price for entry is fantastic, but the total cost to run it and the downtime are more than getting the better car from the start. We are at least $100 into upgrade parts for each car to keep it running.
The driveshaft you need is 16410s that looks similar to the original except with a male stud. Do not get the "u-joint" version, it's slightly too long between the bearing seat and the pin at the diff-cup and will bind up( see picture)
You also need the upgraded diffs because of the additional depth of the slots in the cups (see other picture)