My dad just bought an 02 3500 dually, I have a 1st gen so I know little about them. However it has 90k on her and the tranny fluid was never changed. It hauled a 5k camper on her back most of its life. The truck shifts fine, according to dad. I haven't driven it yet, but the fluid is brown and has a almost burnt smell. He wants to change it and put Amsoil in. I have no luck with automatic trannys, but whenever I've seen this situation before the tranny blew weeks after changing the fluid. Any info is greatly appreciated about this or any thing else I should look for being new to the 24 valves.

 

New to you it's always a good idea to drop the pan, change the filter, check the band adjustments. It will also give you a chance to see the "debris" that has aquired on the magnet. If it's "never" been changed you might be a bit surprised at the amount of gunk on the magnet. If it's all mushy, smooth type of accumulation I'd deem it normal. If you see lots of metal suspended in the fluid, as well as "pieces/chucks" on the mag it may be a sign of excessive wear. Either way, you'll run it until you actually have an issue. Pan gasket should be the re-usable type on that year. Get a new filter, torque the pan bolts to 125 inlb and use ATF+4.