This would not be a simple task. The basic system architecture between the "Premium Sound" and "JBL Audio" systems in a '95 Explorer is TOTALLY different. The radio head units even have a different architecture. The "Premium Sound" head unit uses a remote amp - the "JBL Audio" head unit uses a remote tuner/amp combo.
To do the job right, you would need:
1) a new head unit - Ford/JBL "Digital LUX FCU (Front Control Unit)"
2) a new tuner/amp - Ford/JBL "Digital LUX RCU (Rear Control Unit)"
3) 4 Ford/JBL 5.5" x7.5" satelite speakers (in enclosures)
4) the Ford/JBL Subwoofer enclosure with driver and amp
5) new wiring between the FCU/RCU and the SW pigtail from the RCU to the SW amp
Ford offered a kit for this upgrade at one time, but, they're probably all long-gone by now. Another possible alternative might be to swap the 4 channel amp from your system for a 5 channel (w/SW out) from a Mustang Mach 460 - and use that to send input to an Explorer SW assembly (enclosure w/amp and speaker). The result is unpredictable - you'd likely have more bass because of the sub, but the other 4 channels may not sound right, because the Mustang amp won't be EQ'd to the Explorer interior.
Unless you can find these parts at a Swap Meet or junkyard, your least expensive route may be to just add an aftermarket sub.
Regards,
Cobrajeff
