Jacky,
I think first you need to verify the whole tx and rx system is OK.
- Use the tests on the /test folder: test/can/doc/FSL-UT-CAN-003.txt. This test can help you to verify you have your system correctly. Can you tell how they are working? try 8 bytes.
- check your receiver is working correctly: try another receiver or use loopback mode on imx53 to receive the messages on a different port. Try a know working transmitter.
- What happens if you send less than 8 bytes, like 7, 6, 5, etc?