The RE series of trans, which is 96 and newer, has issues with the electronics on the valve body. Lots of issues on the 44, 46 and 48 versions in the bigger trucks. There are updated replacement parts, check out the diesel forums. And since you said its a 500, I'm assuming its behind a 3.9 V-6? The 5.2 [44re maybe] & 5.9 used the 46, if you have a 4.7 or the v6 version 3.7, you have a totally different trans.