I'm driving a 2N4401 with a 1K....even did a 560 ohm. An open collector config to turn on/off the ground circuit to the relay.

I'm actually using the input to the LM317 on my power supply (around 8 volts) for positive relay voltage. (5v relay)

Using pin D4 on the PIC, which works fine (goes high for 15 seconds) but using the transistor to the relay will just give a momentary pulse and won't engage.

However, if I tie the ground circuit directly and bypass the 4401, the relay works perfectly....so I know the power supply is fine.

Maybe the transistor on resistance is too high but like I say, surely there's a part someone has used to sink 180ma without a problem.