By getting a hexhut hammer with a wooden stabber to poke through the hole.
You need to replace the speed sensor. The speed sensor is mounted in the transmission. It is held in place by one bolt and is very easy to replace. You simply unbolt it, remove it, and reverse the procedure to replace it. The sensor has a wiring connector on it. The sensor should be on the transmission around the area that the drive shaft exits the transmission. It is driven by gears cut into the portion of the drive shaft that is inside the transmission casing. It is on the top of the transmission, above the area that the drive shaft (not sure if it is the left or right drive shaft) exits the transmission.
Its the gear that connects the speed sensor shaft to the transmission
ring on drive shaft with senser next to it. usual fault! cracked by rust ring on drive shaft. change shaft.
The rear, or tail shaft, of a transmission has a seal around the output shaft. The drive shaft will have to be removed and the seal replaced.
In the tail shaft housing. you have to remove the drive shaft and the tail shaft housing to get to it.
on the output shaft of the transmission, close to where the drive shaft enters
To fix the drive shaft on a 1979 Lincoln Town Car, first safely lift the vehicle and secure it on jack stands. Disconnect the drive shaft by removing the bolts at the universal joints and the rear differential. Inspect the drive shaft for any damage; if it's bent or worn, it may need to be replaced. Reinstall the new or repaired drive shaft by aligning it properly and tightening the bolts to the manufacturer's specifications.
On Drive side It's On the bellhousing
The drive shaft does not leak. It is either the pinion seal or the trans. seal. Either one, the drive shaft has to be removed. The rear seal should be done at a garage, but you could do the front.
its behind the OS drive shaft (gearbox side)
It will be screewed into the transfur case tail shaft housing. Where the drive shaft slides into it.
Some vehicles mount a speed sensor on the drive shaft, to see how fast the vehicle is traveling. Not all vehicles use this kind of sensor.