Your 4001 has a .0047uF capacitor in series with the bridge pickup. In the mid-80s RIC took that cap out and replaced it with a wire. Then in 2006 they put in a tone pot with a push/pull switch so you can put the cap in circuit or short it out. When you short the cap out, you get more low frequencies out of the bridge pickup. If you want to see what I mean, take a 1.5" bare wire and find the .0047uF tiny cap going from the bridge pup side of the pickup switch to the treble volume pot and wrap the wire on the leads at both ends of that .0047uF cap and you will be able to hear the difference. This is reversible, and if you like it you can get the 500k pot/switch from the RIC Boutique and mod your 4001. Here is a drawing:
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Oh, and you have a very nice JG bass - I saw the pics a couple pages back. If you want to shine it up to almost like new get some Meguire's Scratch-X 1 (NOT the 2.0) and then use Zymol (the blue stuff) to give it a wet water finish. Use a soft cotton diaper.
http://www.rickresource.com/phpBB3/viewtopic.php?f=14&t=255794