Your '98 has no center differential, so the front and rear wheels are essentially locked together. When you go around a curve, the front and rear wheels must take separate paths and travel different distances from one another. This means that slippage has to occur between the tires and the road surface.
If you're on dirt or a slippery surface you're OK - the slippage can occur with little strain on the drive train. If, however, you're on dry pavement, you're forcing the slippage to occur when there's a great amount of adhesion between tire and road. This creates binding, and creates a huge amount of stress on the entire drive train as it forces the slippage to occur. If you persist in using 4WD on dry pavement, you will cause very rapid wear on the tires and drive train. Eventually something will probably break. If you're lucky, it'll only be a CV joint instead of something really expensive.
I owned a '98 LTD for 5 years. It was a reliable, robust vehicle and gave me 75K miles of trouble-free service in spite of towing a 4,000# trailer much of its life. When I bought it, I was ignorant of the limitations of its primitive 4WD system. I found out about it the first time I tried driving it around on dry pavement in 4WD. Frankly, I always considered it to be a PITA.
Regards.