Are you sure you mean Timecode? This sounds more lika WordClock to me. If so, read on.
Which end has the output -- BNC or XLR? It might also depend on whether the equipment fully conforms to spec and uses transformers, some do short-cuts.
Making these changes without transformers are tricks. They will not work on long length cables and might even with short cables have problems. Quite often they work though. Generally I would not connect pin 1 of the XLR to the BNC except to the shield of the cable. 2 to middle pin of BNC, 3 to shell.
// Gunnar