According to my Haynes Ford Explorer repair manual :
On the 4.0 liter OHV / pushrod style engine , in order to remove the timing chain
cover you have to remove the oil pan which involves removing the engine
The explorer has a timing chain, not a belt.
timing CHAIN
It has a timing chain.
timing chain
Timing CHAIN on the 4.0 liter V6 in a 1993 Ford Explorer
The 98 explorer has three timing chains. The front two can be replaced by removing the fan, fan shroud, serpentine belt and water pump. The rear chain can not be replaced unless the engine is pulled from the explorer to gain access.
You never need to replace the timing chain if the engin use timing chain(not timing belt).
Timing chain.
I am almost certain that the timing chain should last throught the life of the Explorer.
Normally a timing chain will last the life of the engine and is replaced during a complete engine rebuild. No maintenance is normally required.
The 4.0 liter SOHC has ( 3 ) timing CHAINS and if it is 4x4 it has a 4th chain for the balance shaft
I believe the Explorer does NOT use a timing belt, but rather a timing chain