you can remove the screw from the linkage/saver on top of the reverse servo and check and see if it is a servo problem or a transmission issue. you should be able to separate the linkage without removing it from the servo, it has a top and bottom plastic piece and a spring in the middle, you can separate them without doing any damage and it will only go back together 1 way. also if you put a small screwdriver on top of the silver spring and twist it a little the top will come off and not disturb the spring.

hope this helps you find your problem