  Models with varying cosmical parameters, which were earlier regarded
constant, are getting attention. However, different models are usually invoked
to explain the evolution of different parameters. We argue that whatever
physical process is responsible for the evolution of one parameter, should also
be responsible for the evolution of others. This means that the different
parameters are coupled together somehow. Based on this guiding principle, we
investigate a Bianchi type I model with variable $\Lambda$ and $G$, in which
$\Lambda$, $G$ and the shear parameter $\sigma^2$, all are coupled. It is
interesting that the resulting model reduces to the FLRW model for large $t$
with $G$ approaching a constant.
