Having a Ball
How often should a ball differential be rebuilt? I see guys at the track doing
it all the time, but I just play with my car and it seems fine, even though I’ve
never had it apart.
Ain’t broke, don’t fix. A ball diff can go a long time between rebuilds as long
as it is kept properly adjusted. Slipping due to a too-loose setting is what
kills ball differentials. If your car screeches or barks when you accelerate, it’s
restore like-new performance.
parts list in
likely the differential slipping. If left unchecked, the diff balls will score the
diff rings. Then you’ve got a vicious cycle of rough rings damaging the balls,
which causes more damage to the rings, which eats up the balls...and then
you need to rebuild. If your diff turns easily, doesn’t feel gritty when operated by hand, and doesn’t slip in use, then keep driving. If not, rebuild it with
fresh rings and balls. A complete rebuild kit will only cost you about $15.
It’s normal for the diff balls to
polish a bright line on the diff
rings. If you can feel a groove,
the ring is worn. Flip it over
to reveal a fresh surface, or
Must-Know LiPo Info
What does it mean to “balance” a battery pack?
“Balancing” is a term used when charging LiPo batteries. When a pack is
“balanced,” it means the cells have the same voltage. For example, a 2-cell,
7.4-volt pack is balanced if both cells have 3. 7 volts. If you don’t balance the
cells, their voltages may drift after a few charge/discharge cycles. Why does
this matter? Because LiPo cells don’t tolerate well being overdischarged. For
this reason, modern speed controls have low-voltage detection systems to
prevent the pack’s total voltage from dropping past a certain point (let’s say it's
3. 3 volts per cell, or 6. 6 volts for a 2-cell pack). However, the speed control only
“sees” the total voltage of the battery, not the voltage of each individual cell.
So if the pack is unbalanced, that 6. 6 volts might not represent 3. 3 volts per
The small white connector
you’ll find on most LiPo
packs is the “balance
plug.” It’s wired so that
the charger can read each
cell’s voltage individually
and charge accordingly.
Depending on your
charger, there may be
a built-in balance-plug
port or an external
cell; you might have one cell at 3. 6 volts and another at 3 volts—that
cell will be overdischarged, and now your pack is compromised or even
ruined. Balancing ensures the cells always have equal voltage. Happily,
balancing is easy to do; in most cases, all you have to do is make certain
the pack’s balance plug is plugged into the charger.