I just got a 1998 Land Rover Disco LE, has 119,000 miles on it. The person that had it before me was using synthetic blend, I want to go to full synthetic. Do I still need to flush the engine with ATF before converting? Also, I had a hard time switching the diff. lock from high to low, and vice versa, Is it pretty simple to change that oil as well? Any other maintainance suggestions that I should do to the car? Any help greatly appreciatted. Had the car about a day now, and already in love.e

 

What does the inside of your oil fill cap look like? If it still has alot of build up, I would flush the engine.
As for the t/case and it's shifting issues, it is not your fluids, it is the linkage. Work on shifting it every day till it loosens up then shift it at least once a month to keep it moving freely.
If you are going to synthetic, go all the way to slow down the wear factor, diffs, t/case, p/s and brake fluid.