I need to fill and seal between my asphalt driveway and concrete garage floor. Over the years a gap of various widths as developed between them. In the winter the wet ground under the garage freezes and lifts a portion of the garage floor. Is there a self leveling asphalt sealant that I can buy to fill the gap. The gap can be has wide as 3" and in some places 2" deep

 

The most common product to use there is a self-leveling polyurethane concrete expansion joint sealant. (like Loctite S20) You would clean out the joint with a wire brush and compressed air, then fill the bottom of the joint with a foam backer rod, or use foam expansion joint cut to fit. Clean silica sand might be best if it's too irregular to fit foam... either way, your goal is filling the joint so that the sealant will fill the top 1/4"-1/2" of the joint... no more, no less.

Keep in mind that self-levelling means just that. If your driveway slopes, the self levelling sealant will be like a gooey runaway train. Clean silica sand can be use to help dam up areas where you don't want the sealant to run. It takes several days to cure so you may not want to drive over it, and protect it by laying plywood (or similar) over it.

A good commercial asphalt crack sealant (something like this) would probably be hard to find and would cost a small fortune.