Speedo Cable

Yes I've lubed a few a-body speedo cables.
DISCONNECT THE NEGATIVE BATTERY CABLE !
If you remove the column cover ( 4 phillips screws ) you can get some light in where it connects to the instrument. It will have a hex collecter screwed on the end just like the one on the trans end or it will have a plastic end with a hooking keeper that is similar to one half of a wooden clothes line pin.
I have removed the one screw holding the fuse box to the dash for hand /arm room.
Once the cable housing is off the gauge you can reroute it down toward the pedal area. Grab the cable end with needle nose pliers and pull it out of the sheath. I use white litium to lube the cable between 2 fingers as I work it back into the sheath.
Now the hard part... the sheath turns nearly a 90 degree radius under the drivers seat and the end doesn't want to go around it on the way back in. It will but it can be a fight. Right there is where the bounce is generated too. I've seen the cable woren through the sheath in that corner.
Anyway... clean all the excess grease from the connecting end cavity with a tooth pick or something so you don't get too much grease in the instrument.
Route it back up there the way it was and reconnect it.
Alternatively there are zerk fittings especially made to screw on the sheath collector at the trans end. With that you can use a grease gun to inject 3 or 4 pump strokes. Finding a service tech today that has one of those zerk adapters might be a challenge. Hope this helps