Mazda sucks! This problem actually started just beyond the warranty period. Slight shudder in transmission. When shifting manually, no issue.

Dealership advised that they've seen it, and a trans flush resolves the issue, at my expense of course. I tried it against my better judgement, all be damned they were right. They said to flush it every 40k miles (against owner manual recommendation). I did it every 30. Problem resurfaced, got worse and worse with age. Took it to a tranny specialist @ 90k miles and they said my torque converter is shot. Would need to be rebuilt, no use in swapping out because the junk yard ones would have the same problem.

So here I am at 125k miles, driving the car a specific way in automatic (gunning it and keeping RPM > 2k, or I drive it in manual, which is a pain in the ass. Car has been just about flawless other than this BIG issue.

Won't buy another Mazda again. Piss poor.