Car Jerks during downshift from overdrive

[LVcountryboy]

Hey, hopefully someone can help me out. I have a 98 GST Auto. When driving my car around town, everything shifts fine, up and down. But as soon as i get on the highway, driving at highway speeds of 65+mph for over 10 minutes (problem doesn't arrise after short highway trips), when i come to a stop (a gradual slow stop) at around 10mph the car jerks as it downshifts from what i assume to be OD to maybe 1st. But it only does this when i've been driving highway speeds in OD for long periods of time.

Also, with this, after being on highway speeds in OD for long periods of time, if i punch the throttle to try and accelerate, the car violently shifts down, and then goes. One time during the downshift to pass a car, the car acted as if when it down shifted, it got hung up in neutral, as my rpm shot to 7000, and stayed there for a few seconds while my car wasn't picking up any speed, and i was only at 60mph when this happen. Then after those few seconds the rpm came back down to around 4-5K and car accelerated as normal. Any ideas to what is causing this? I know there should be a little small jerk of some sort in automatics when the car downshifts to pass someone, but nothing this violent.

Thanks

 

[LVcountryboy]

So I take it no one has any ideas?

 

[reno23]

Have you done your basic maintenance on the a/t, ie. filter and fluid? I had similar issues and after basic maint. I got six months of trouble free until I needed a rebuild.

There is more info similar to what your describing, when I searched I found a lot other than this:

http://www.dsmtuners.com/forums/newbie-forum/334144-auto-no-3rd-reverse.html#post151841371