2001 Nissan Maxima. This has happened twice in the last week. After driving for about an hour in hot weather, the tranny "slips" while in drive. RPM's will go up and car will not advance. If i put the car in low gear, it will drive. But, in "D", it won't go - the engine just races. When cooled down, the car drives normally in "D". 149K miles. Any help/suggestions are greatly appreciated.