It’s been a few weeks since I got the BZ Master and, while I originally intended to provide lots of content, showing me building and tuning the car, I’ve spent the little free time I’ve had driving it. I do want to go back and touch on one thing that I thought was interesting though and that is the ball diffs.
If you own a BZ3, BZ5 or even an SZ2, the diffs probably look familiar. While Atomic has tweaked things a bit over the years, the basic design hasn’t changed much. Needless to say, I was a bit surprised to see that one of the diff halves was now aluminum. With the SZ2 and BZ5, this piece came with the aluminum diff upgrade. Score!
For my build, I opted to upgrade the other half of the diff to aluminum. The rest of the diff, including the pulleys, were parts included with the diff.
I decided not to use the dust proof pulleys because of difference in offset. The stock pulleys have worked great so far but I may go back and try them at a later date.
Smooth diffs is key to having a good driving AWD car and that begins with sanding your diff rings. Atomic includes a tiny piece of 1500 sandpaper which will do in a pinch but I like to use half sheets of 1000 and 1500 sandpaper when building mine. I’ll hit the diff rings with the 1000 grit to get them flat and then 1500 to get them smooth. I do the same thing with the thrust bearing rings. The ones that came with the BZ Master had some sort of ink on them so I sanded them down until the ink was gone.
Before installing your diff plates, take a look at the outer edge. These plates are die cut and sometimes there is a rough spot that sticks out far enough that it rubs on the pulley. If you find one, hit it with some sandpaper until you can’t feel it anymore. Thankfully, this wasn’t the case with the BZ Master.
While I use a good amount of black grease in the thrust bearing, I don’t use a lot of grease on the diff balls nor do I put any grease on the plates. Usually, I put some grease in the palm of my hand, drop the diff balls in it and make sure they are thoroughly covered. This way, the diff rotates smoothly, yet there isn’t so much grease that it slips.
Hopefully this helps in some way. I’ve put A LOT of laps on my BZ Master over the last few weeks and the diffs have remained as smooth as when I built them.