1998 Toyota Corolla LH loud pop/vibration when accelerating

Hello, have read over many of the very helpfull how-to/what to look for/how to diagnose threads, but couldn't find my particular situation. So, guess u can see it's a 98 4cyl Toyota Carolla w/ 258000 miles. No major repairs to date, but about a week ago I'd just gotten on an interstate on ramp, starting to accelerate when pow, then a crazy vibration. Sped up and still popping. Let off and after a few secs it stops. Through the next nine miles it would come and go at different speeds for less than a min each time, then fine for a few miles. I assumed the cv axles. So, took it next day to drivetrain shop where they have a mechanic who's dedicated to cv axles only for years now, so I trust his advice. Told him what happened, where you hear loud pop(or knock). Said go ahead and check both sides. He can go through them so fast, I basically gave him $25 for labor to rebuild my cv axle and reinstall. He did rebuild a cv axle, just the RH side. He told me he'd checked the driver's side cv axle but it was fine. Drove away, pop still there(all speeds), sperts of crazy vibration kinda come and go. Started noticing that the pop would start as I accelerated up inclines, and the times it was already popping when u started climbing a hill the noises got worse, until u reached the summit and u could ease the gas back. So, took it back to him and after checking it again I was told that the axle is fine. Now tonite while playing with steering wheel I noticed the knocking stops when you begin to turn either left or right. So I always had thought and read that the cv axle will pop worse during turns. I've replaced them in a 96 maxima, a 95 civic, and a Honda prelude, and all of those repairs indicated by a upop while turning steering wheel. I still feel like it's the axle, even though my expert doesn't think so. He said to get my struts checked, but I haven't had time yet. This has been going on bout a week now, seems to be getting worse. What should I begin with next? If I don't know I will read and learn. Just need apush in the right direction. Thanks in advance.