The B44.3 featured gear diffs, but I think to fit these on the 44.1 you also need different gear casings and perhaps more. BugleBoy Racing also had a conversion that allows you to fit DEX410 gear diffs:
http://bugleboyracing.com/index.php?productid=20
Honestly though, I'm not sure the ball diff is actually the problem. The B44's drivetrain was conceived in the era of brushed motors where lightweight was more important. The gear casing is relatively thin by modern standards, so under (heavy) power it may flex to an extent that the mesh is poor, wearing quickly or even stripping teeth. You could try shimming the gears (toward each other) so that the mesh is a little tighter, hence if there is flex the mesh is better.
When shimming the gears, pay attention that the gears still move freely and are not pushing against each other, as this will limit the service life of your ball bearings particularly, but possibly the gears too.