re: Filling Joints in Concrete Drive

Self leveling sealant is the way to go.

Remove top layer of wood and use fine mason sand to seal and fill large voids. This way your caulk doesn't just drain into the cracks.

Be careful using the sealant you can make a pretty big mess with it. Always keep a rag so you can catch runoff from the tip and spend some decent coin on a good quality quart tube caulk gun (concrete supply store).

If the wood is anywhere near your house or up against it pull it out as it attracts termites.

Back in the day everyone used true redwood and that was a lifetime product. Redwood is so scarce and expensive you hardly see it on fascia anymore, much less as expansion joint material in paving.