Hi MyDiablo84. Welcome to the forum. I suspect your transmission is going into second gear and staying there. If it stays in that one gear unless you turn off the ignition switch and restart the engine, it is going into "limp-in" mode which allows you to drive it slowly to a repair shop.
In general, if it goes to limp-in as soon as you start the engine, (you would notice real low power starting from stop), or while you're cruising at a steady speed, it is more likely to be a sensor-related issue. If it goes to limp-in immediately after or during a gear change, typically an upshift under light load, it is more likely to be slippage in one of the clutch packs inside the transmission. Your mechanic or a transmission specialist will use a scanner that can access the transmission computer and will read the "clutch volume index". That is a set of four numbers corresponding to the four clutch packs that show how many ccs of fluid it takes to apply each one. Experienced professionals will recognize any that are very high indicating the clutch plates are worn out.
Also, once it went to limp-in, there will be diagnostic fault codes memorized in the transmission computer. Those codes will provide valuable diagnostic information. It is important to not disconnect the battery until those codes have been read, otherwise they will be erased and the information will be lost.
Thursday, June 17th, 2010 AT 2:53 AM