New 08 Elantra SE auto transmission frequent skip up/down at appx 30 mph ?

I just purchased a new 08 Elantra SE. Delivered with ~400 miles, and I've put ~100 miles on it in the last 10 days. 85% city driving 25-40 mph, and 15% highway on 3 occassions at 55-60.
Driving 3 miles to/from work twice daily (12 miles total each day), on fully level grade (no hills anywhere), somewhere between 25 and a little over 30, but even at a constant speed, the transmission wants to shift up a gear, the RPMs drop a bit, then shortly thereafter it feels like it's shifting down a gear and RPMs increase a bit, only to later go back the other way.
It causes a jello like forward/back wiggle feeling. It's like it can't decide which gear to stay in. It's not noisy or significantly tugging, just very sloppy and wiggly, and therefore annoying, vs. smooth and constant.
To rule out my own foot movements, I even tried cruise control on multiple days at 30, 31 or 29 mph (since it's a safe low traffic and no stop road for 2 of the miles) and it still exhibits this tendency to 'slip' up and down right at this speed with no change in grade or road surface.
I have not noticed this at any other speed, but admittedly haven't driven much at a constant speed other than 25-30. I did not recall this feeling in the GLS we test drove before we bought the SE they had to transfer in, but it's hard to remember what all we felt with the GLS.
Any suggestions? Will this 'fix' itself based on the learning mode? Is this a simple software adjustment or is there something mechanically wrong with my new car? Or is this just the way it works in this model?
I've driven 8 years over the same route in a Cavalier and never felt this same tugging/release during the trip, and also didn't notice it for 2 weeks of driving in our 05 V6 Tucson, so it was clearly noteiceable as soon as I got the Elantra.
Thanks for any input.
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If I had to hazard a guess, I'd suppose that it's engaging/disengaging the torque converter clutch.
If it's not intrusive, have the dealer look at it when it's time for your next oil change. Don't mention anything about the torque converter clutch. You've given an excellent description; provide that to the dealer. Let them determine the cause.
There are currently no reprograms available, but as long as the throttle position sensor and speed sensors are operating properly, reprogramming is probably the only practical way to address this issue.
If the dealer reports that it's normal and you're not satisfied with that, contact Hyundai consumer assistance. If Hyundai becomes aware of enough customers who experience this issue, they may develop a reprogram (if they're not working on one already).
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