The first hop-up for an AWD Mini Z should always be
bearings. In this case we chose
AtomicMods ceramic bearing set. Although a little pricey in contrast to other types, these are smooth as silk and free as can be; definitely worth the extra money.
Replacing the bearings is a very easy task to do. The only tricky part is installing the main drive shaft bearings. To make this easier make sure you start with the rear one first. Take the rear section of the car off, remove the spur gear and pull the shaft out (you might need to use a set of pliers to do this). It should be easy to take the rear bushing off by gently prying it with the shaft you just removed. As for the front, if you remove the top cover, the pinion and bushing should already be loose inside the gear case.
To install them, start by sliding the spur gear onto the shaft. Slide the rear drive shaft bearing over the shaft and insert it into the chassis towards the front. For the front bearing, remove the front differential and then slide the bearing over the shaft, making sure the bearing seats in its place. After this is done, simply re-install the pinion by pressing it onto the shaft.
After bearings, the next most important part of the drive train to upgrade is the differentials. Ball differentials are essential in this chassis. The stock differentials on the car are not only weak, but act inconsistent due to the ease with which they unload under hard cornering (this refers to the effect with which all power goes to the tire which does not have the cornering load). We love
Atomic's adjustable plastic differentials. The ease of adjustability as well as their smoothness are tough to beat.
Set your front differential slightly loose (but not slipping) to provide enough entry steering into the corner. Don't go overboard though, if the differential is too loose in the front the car will understeer exiting corners due to slippage.
In the rear, tighten the differential until the point where it will no longer slip under hard load (such as high speed sweepers and corner exits on tight hairpins). If set properly, the rear diff should allow you to be very aggressive on-throttle out of the corners, allowing you to take full advantage of the AWD's acceleration prowess.
Finish the drive train upgrades with a set of high-quality
aluminum or
titanium drive shafts. The stock units will not withstand much load and will drive you crazy trying to figure out what is wrong with the car if one of these goes bad. Adding these will totally bullet-proof your drive train.