I don't know much a bout transmissions but I think I may have a problem with my auto 91 RS 305. For instance, if I start accelerating at about 2300 RPM, within a few seconds their will be a small thump and the RPM will suddenly drop down to about 1200 RPM, all the while the pedal is in the same position. To get it out of this, I have to press down on the pedal a little more, it stays at 1200 until a few seconds later then thumps again and the RPM suddenly rises to 2300-2500 RPM. My car DOES seem to be slower than it should. Is this a transmission problem? And if so, is it a little problem or a BIG $$$$ problem??