Gusse,

You was rigth! My problem was grounding between PICs. My wiring was wrong! Sorry!
Using a 1k to 10k resistor between Tx(5v) and Rx(3,3v) it is working fine.
Then, I put 2 diodes without resistor and doesn't work. I removed 1 diode and works fine. Then I puted a 10k + 1n4007 and works fine too.
I tried with 2 diodes 1N4148 but its fail. Using just 1 signal diode fail also.
Now my circuit is 10k resistor in serie with 1 diode 1N4007! Do you think it is ok?
Thanks again!