Almost all the heat in a tranny will come from the torque converter and the lock up clutch inside it. Being summer time now everything may feel fine as you drive it but do a "test" the next time the tranny's warm. At full lock up accelerate kinda hard, not hard enough to kick down, but hard enough to see if the tach on the motor increases out of sync with the speedo. If it does then your torque converter is on its way out and overheating the tranny. Sometimes at the end of this test you'll even feel the trans and motor sync back as the lock up clutch will hold at the lower stress. This test by no means rules out the number 4 clutch pack I'm afraid as both are used in conjunction for overdrive.
Last edited by BigFuel; 06-08-2012 at 04:26 PM.