These should be wired to a 3.3V CAN transceiver...
Please add parts you are using successfully with Teensy 3.1 to this list.
TI SN65HVD230D on 3.3V (1MBPS)
TI SN65HVD232D / SN65HVD232QDQ1 on 3.3V (1MBPS)
NXP TJA1050T/VM,118 on the same 5V supply as the Teensy. (1MBPS)
Microchip MCP2551 on 5V (reported at 500KBPS)
Linear LT1796 on 5V (not speedtested)