Hi there,
Make sure the oil level is correct, and if the transmission oil is dark get it changed and the filter as well. There may be a sticky shift valve in the main valve body. An accredited transmission shop will be able to do a line pressure test on the transmission and also check for trans fault codes. I would get it tested sooner rather than later, as transmissions can be very expensive things to repair, and if there is a problem sooner will be cheaper than later.
Mark (mhpautos) :D
Saturday, December 8th, 2007 AT 9:10 PM