today i was driving at 40mph when suddenly the car had a big jerk and it shifted into 4th automatically. the shift was not the regular smooth shift either, there was a big THUD and down to 4th. what could this mean? this happened yesterday as well on the highway at 60mph. there are no mods on the car and it has 70k miles it is 2002. i always use the tiptronic ALWAYS and this never happened before. i usually shift up at less than 2000 rpm. usually the minimum speed required to shift up is when i shift. is it something im doing wrong? tranny fluid has been changed at 63k.

does this sound like the torque converter locking up?
i read online that the tip usually goes haywire after sometime and a simple battery disconnect should resolve it. i hope so. i will do that at night.

any type of help is considered great. thanks guys!

 

Best thing to do would be to check atf fluid levels. The torque converter is locked from 3rd gear and up, so its not the torque converter... You really need to check the fluid level though, I wouldn't drive it much if there was such a big thud and jerk as you say, you could end up destroying the transmission and even worse it could lock up and then damage your engine too...