lock-up ?
Thats easy. To the layperson however, it can easily be mistaken as what feels like another upshift. If your car is tuned properly, around 48 mph at normal driving you should feel the car "bog" as if its shifting, and you'll see the tach drop to anything from 1400 to 2000 rpms, depending on what type of gears you have. When this happens, if you slowly lay into the gas and the rpms raise in a linear fashion (linear is the key) with regards to engine speed (think of a linear graph of RPMs and MPH), your converter is locked. A good rule of thumb is this: if you have a car with a 2.73 rear and you are driving at 60 mph, your tach should read 1500 rpms if you are driving with normal throttle and a locked converter. If you have a 3.42 rear and you are driving at 60 mph, your tach should read about 2000 rpms if you are driving with normal throttle and a locked converter. Hope that helped you out.
