F22raptor

I have a 93 ls400 the speedo has stopped but the odo and everything else still work I have Been told this is the speed sensor connected to the gear box is this correct is there a way to trouble shoot this without spending ***** loads of money if this is the case where about on the box is it located and what is te oem part number for the item ... I live in Australia so is there any after market brands of this item I can't seem to find them in Australia