Girlfriend's '04 Hyundai Santa Fe (64k miles) with 4-cylinder engine was exhibiting some shift slipping around the 35-40 mph range (prob 1st-2nd gear). Upon inspection the fluid was pretty burnt and nasty.
Did a transmission fluid change, got a lot of gunk out of the trans via the magnetic drain plug, did not see any large metal pieces, and replaced the fluid with the proper Hyundai fluid, filled and checked level hot, cold, and a few days later.
A few days later the shift slippage has gotten MUCH harsher in the same range on heavy acceleration -- NOT evident in normal driving but mostly when you have to punch it, like to merge onto the Interstate, etc.
It reminds me of the probs. with the 2nd gear I used to see in the old Saturn S-series cars...Valve bore gets scored, fluid slips around bore, then when enough pressure builds up, SLAM, transmission shifts.
Anyone seen anything like this on the Hyundais? Am I looking at a valve body job, and where to get a good rebuilt one? My usual source (valvebodypro.com) doesn't seem to do Hyundai.