I recently purchased a use 2004 3500 dually 4x4 with 138,000 miles.
The tranny fluid smells a little burnt. Should just drop the pan and replace the filter and the 6 qts in the pan? Or should I drop the pan, replace the filter and do a fluid exchange by disconnecting the cooler return line.
Please give me your opinions, I am new to Dodges and want to do the right thing for my tranny.
Thanks.

 

Do everything you can, you'll feel better about it. When I did mine, I threw in a new filter, and some other little electric parts that are in there along with a double deep pan to increase the interval between servicing.

If you don't know when it was done last, then you should consider that you may be doing this for the first time on the truck.

Do a search for this topic, and you'll get back hrs and hrs of reading. This site has a lot of information about when, what, and why to do things to your truck