Get a transmission cooler installed, a transmission temperature gauge installed, and a deep aluminum pan for the transmission installed. Use a good quality synthetic transmission fluid compatible with the owners manual specs.
This is probably an AOD transmission and they have a drain plug in the converter, change ALL of the fluid when you do it.
This will go a long way toward preserving the transmission and extending its life. Cooler is better.
Charles
2007 Winnebago View 523H on a 2006 Dodge (Daimler-Chrysler aka Mercedes) Sprinter 3500 chassis. Bought Sept 2015 with 18K miles on it, Prog Ind HW30C, Prog Dymanics PD4645, Chill Grille, PML/Yourcovers.com deep alum trans pan, AutoMeter 8558 trans temp gauge, Roadmaster sway bar, Fantastic Ultra Breeze hood, added OEM parabolic mirrors and RH aspherical mirror.