Hyundai Repair: RPMs Shoot Up During Acceleration, mile powertrain warranty, hyundai accent

Question
Hi, I own a 2007 Hyundai Accent GLS, automatic with 73k original miles on it.  Two weeks ago I had the timing belt and the rest of the belts changed as well as a coil.  Since then, when I hit the gas hard to accelerate the car seems to almost go into neutral and the RPMs will shoot up to near redline.  Then it will slam back into gear and hit noticeably hard that passengers even notice it.  This has happened about 4 times and at varying speeds.  I can't duplicate the problem as it seems pretty random.  Any idea what this could be?  I want to avoid paying dealer prices for dignostic if I don't have to.  

Thanks!

Lou

Answer
This sounds to be a transmission related issue.  I doubt you'll find anything, but as always, I'd recommend starting with checking the diagnostic trouble codes.  If nothing is found, the transmission adaptive values (basically, the shift logic to make shifts smooth and precise) will probably need to be relearned.  Most likely the dealer will be the only place able to do this.  

My best guess is that you'll need a transmission replacement.  If you're the original owner, this repair will still be covered under the factory 10 year/100,000 mile powertrain warranty.