I have a 1987 Jeep Cherokee that has 220,000 miles on it. I use fully synthetic oil in the engine, but the rest of the vehicle uses conventional fluids. I've been told that the Jeep is too old to switch over all the conventional fluids, to synthetic; switching could cause more harm than good. Other opinions say that you can switch at any time. I'd like to keep this vehicle on the road as long as possible. I am mostly interested in possibly switching the ATF, differential fluids (front & back), and the transfer case. So, does anyone have any opinions? Thanks in advance!