If you have an older bachmann engine where the tender hooks to the engine and the pin is plastic ,the new all wheel pickup on the new tender is useless. Answer hardwire, which makes a stiff connection and it still doesent run right. Not to mention the decoder wires also.
I suggest you find better wire. Minitronics and others have super flexible wire that while still not as free as the drawbar post type connection, works very well.
The current DCC loco's use flexible wire with laquer insulation instead of vinyl to help with flexibility.