Sam,
before rushing out and spending money on a new transformer, try a few things first.
create a simple circle of track with with two wired lockons
try your 2-8-0 and 4-4-2 on that small loop
let us know how they run.
also it might be very helpful to know the following:
are you running on carpet?
which specific engines are you running, the 2-8-0 and the 4-4-2?
what diameter is you circle? 36, 42, 54.....
What lighted passenger cars are you running O27? scale?
what gauge wire are you running from transformer to track?
Do you have a multimeter?
BTW the CW80 is not the best transformer but it's better than most think it is.