speedo

yesterday i heard a noise coming from my speedometer area. i read in my service manual that theres a flexible cable that enters the speedometer driven gear in the transmission on one end and the speedometer head on the other end rotates both mechanisms whenever the transmission main shaft, propeller shaft and wheel rotate. would lubricating the speedometer cable going into it stop the noise, what should i use to do it with and do i have to pull the cable out of the speedo to do it? it's in a 70 GTO.
thanks,Jim