Adjusting bands has been asked & answered.
Regarding synthetic ATF... . It will not void warranty. There is a federal law - Magnesson-Moss Act of 1975 - that says for a mgf to require you to use only their lubricant, to maintain waranty, they must provide it free of charge. Dodge can only void a warranty if they can prove the fluid you used caused the problem. Some dealer reps will try to tell you differently but if you ask for it in writting they will backpeddle quickly. Sytnthetic ATF, as long as it meets or exceeds Mercon 3 specs. will do your transmission a big favor. Works better when cold - and a lot better when fluid is hot, say over 200 degrees. Synthetics ATF lasts longer (35,000 +/- if towing and 50,000 mi if not) and will not coke up when you drive it hard.