I recently purchased a 2000 SC2 with 1.9 DOHC engine, auto transaxial. The last week or so when driving down highway it feels and sounds like it is shifting in and out of lockup. Only last about 5 to 20 seconds. Tach increases 100 to 200 RPM and then feels like it goes back into lockup. Shifts great in all gears with no reverse slam. Does this on flat ground or going up and down hills. Does it in or out of cruise control. I just changed fluid and filter when it started doing this. Fluid and filter had been changed about 20,000 miles ago according to Carfax. Fluid was very clean, not burnt, and no filings on magnet. Could this be a sensor and does anyone have any ideas. Car has 115,000 miles on it

 

Had a '98 SL2 that did the same thing. Fortunately for me, it started happening while the powertrain warranty was still in effect. Took a bunch of bitching on my part, and some directed letters from the regional manager, but they finally replaced the transaxle in its entirety ... problem solved