My 91, 4 Matic light just came on at 110,000. The manual says to disengage the 4matic function by putting the control lever in the test position and take it to a dealer. I've check the hydraulic fluid level and that's all I know to do at this point. Any experience out there with what typically goes wrong? I hate to take it to the dealer without some knowledge before hand. And I do not want to start randomly replacing componets. All help is appreciated.