The earliest known production 4003 was born, sporting a revised truss rod system (adjusted at body end), features split pickguard and unlike the 4001, does not have a skunk stripe. 
Open-backed Schaller-made chrome tuners replaced the old nickel-plated Kluson tuners. 
The truss rod adjustments now moved to the headstock end of the neck and the discontinued need for a split pickguard. 
The CNC machine is put to full use by carving bodies throughout most Rickenbacker guitars and basses. This increased consistency between like-models moving forward. Starting at this point, there is a carved gap at the end of the fretboard to the end of the neck pickup cavity. 
Walnut headstock wings return after being absent for decades, previously last seen on 4001 basses from 1972 and never before used on 4003's. 2006
Early 2006 The treble tone knob circuitry updated to include a push-pull pot to engage and disengage a 0.0047uF capacitor, enabling a vintage sound found in original 4001 circuitry.
Fall of 2006 
Adjustable poles became standard on the hi gain pickups.
The inset poured resin inlays used since 1973 are replaced with full width plastic inserts. 
The neck design updated to be a two piece neck, enabling a stronger structure. 
Conversion varnish ceased to be used in favor of a UV-cured finish. 
Caribbean rosewood (chechen) replaces African rosewood (bubinga) for the fretboard material. 
The 4003W variant is introduced featuring walnut body rings and a maple neck and matching maple fretboard 
The 4003S and 4003SW were introduced, being a more simple variant of the 4003 and 4003W (respectively) with dot inlays, no body binding, and mono output. 
The pickguard shape is revised, more contoured to the edge of the body 
After decades of use, the original basic design of the tailpiece was replaced with the "v2" tailpiece which allows individual saddle height adjustments and is not prone to "tail lift." 
The silver top knobs introduced in the mid 1960's are replaced with an all-black knob, previously known for use on Rose Morris RM1999 basses and corresponding reissues. 2021
August Rickenbacker temporarily did not use a glossy finish on the fretboards commonly referred to as unfinished, they resumed a glossy varnish in September of 2022.
2022
January Formal announcement made that moving forward all 4000 series basses would feature the single dual-action truss rod
February 
The "skunk stripe" is revived after decades of absence, never before used on a 4003.
September Fretboards resumed having a glossy varnish after about a year of being "unfinished."
A new "D"-shaped neck profile replaces the older, bulkier "C"-shaped profile. 
Rickenbacker introduces the new bridge pickup surround which eliminates the plastic chrome covers used since 1968 
The vintage style knobs changed, featuring sharper edges and a thicker indicator line 