THE ZD RACING EX16 is an awesome looking little RC Car and has nice components especially if you look at the pro variant with discrete electronics. The most glaringly bad aspect of this car however is the driveline which binds terribly. Left as is it will put unnecessary strain on motor, esc, battery and will reduce acceleration, top speed and battery life as well as causing the car to run hot. The root cause took me a while to troubleshoot but I found it and have come up with a fix that means you don't have to pull the car apart.
This is the second of a 3 part series of tuning guides for the ZD Racing EX16. The others can be found here:
What is the cause of the binding?
There is binding in both the front and rear gearboxes, ZD racing have got their tolerances only a little out but enough to cause problems. The problems both front and rear (gearboxes are identical) is that the bevel pinion from the 4wd prop shaft is pushing too hard against the crown gear (forward pressure in the front and rearward pressure in the rear). I can see why they have done this - to maximise engagement between these gears but I think they have overcompensated though and have caused the tight driveline. As you can see they have done a good job with greasing so adding more will not help
As you can see above I took my car all the way apart to find the true cause of the binding so that you don't have to...
Fixing the driveline
Let's get straight into it. I pulled my car right apart to figure out the root cause of the issue so that you don't have to but you will need to follow my instructions closely.
Repeat the process for the rear which is a mirror image of the front except that you don't have to deal with removing and reinstalling a bumper
Don't stress to much about the missing screws, the rigid aluminium top plate means there is still plenty of strength and rigidity with just the two screws coming up from the chassis. The end result is a driveline with the friction gone. The easiest way to compare the improvement is to remove the pinion gear from the motor before you start and try rolling it. Once you have completed the steps above try repeating to make sure you have the benefits. Feel free to tweak the amount of turns you loosen the diff housing screws to get this right for you.
Finally, it is worth considering the ZD racing may have made these tolerances tight to allow for some wear in the drive train meaning it would relax to have less bind after time. I'll keep an eye on my own car and report back here to see if the driveline eases up over time and I can put the front and rear screws from the chassis to the diff housings back in and will report back here.
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