We discuss the mass splitting between the the top and bottom quarks in a
technicolor scenario. The model proposed here contains a left-right electroweak
gauge group. An extended technicolor group and mirror fermions are introduced.
The top-bottom quark mass splitting turns out to be intimately connected to the
breaking of the left-right gauge symmetry. Weak isospin violation occurs within
the experimental limits.Comment: Changes are made in sections I, II and IV; an new figure added;
results unchanged; accepted for publication in Int. J. Mod. Phys.