Unfortunately I have yet to figure a way to get the rear servo apart on a V8 904. They use a double wrap rear band and a different lever than a slant trans and it's so fat you can't get it apart without pulling the pin that holds everything together. You can pull the pin with the trans in the car if you remove the extension housing but it's darn near impossible to keep things in place and when they fall out of place nearly impossible to get re-assembled without complete disassembly so you can get at everything. As Greg mentioned (and I should have mentioned) check the fluid level (in neutral) first to make sure it's correct and go from there. Hopefully it'll be low fluid or a band way out of adjustment