For Q45 owners with active suspension looking to lower and/or overhaul worn stock suspension, but don't want to install coilovers due to diminished ride quality (added stiffness/harshness), there is another option. Shocks and springs are much more time and labor intensive and the cost(s) vary depending on where you source the parts, but I feel that the end result is overall a better option. I used a combination of infinitipartsdeal.com, nissanpartsdeal.com, fromjapan.co.jp/en/, blackhawkjapan.com, rhdjapan.com, rockauto.com, partsgeek.com and ebay.com to source the necessary parts due to price or availability.
NSC6004 (KYB SR SPECIAL FRONT STRUT SHOCK ABSORBER) x2
N183D (RS-R DOWN SUSPENSION FULL SET)
54302-3H920 (Strut Kit-Front Suspension,RH) x1 REUSE
54303-3H920 (Strut Kit-Front Suspension,LH) x1 REUSE
54330-4P000 (Cap-Front Strut Insulator) x2
54329-10V00 (Spacer-Front Strut Insulator) x2
54320-3H900 (Insulator Assy-Strut Mounting) x2
54322-4P701 (Bracket-Front Strut Mounting Insulator) x2
54325-4P001 (Bearing-Strut Mounting) x2
54040-4P001 (Seat Assy-Front Spring, Upper) x2
54050-4P702 (Bumper Assy-Bound) x2
54034-4P000 (Seat-Rubber, Front Spring) x2
55031-6P100 (Tube-Spring) x2 REUSE IF POSSIBLE
My one owner 2001 Q45t has 105,000 original miles, so I was able to reuse some of the original parts. For people with cars that have significantly more miles or wear, you should expect to buy new tube springs (55031-6P100).
There are cheaper strut mount (54320-3H900) options, which include the strut bearing (54325-4P001), on rockauto.com. I personally used GABRIEL (143210) strut mounts, but opted to use the OEM strut bearings (54325-4P001) due to quality. According to the photo, the KYB (SM5328) strut mounts seem to include a better strut bearing than the one provided by GABRIEL making them potentially a better option.
When uninstalling the whole OEM strut bodies (54302-3H920 & 54303-3H920), I had issues unbolting the nuts on the stabilizer bar end links (54618-6P001 & 54668-6P001) on both sides; I had to cut one of the nuts off and use a dye to clean the threads. It might be a good idea to replace these, especially if you run into problems like I did. With everything disassembled, I took the opportunity to replace the ball joints with a pair of new old stock MOOG K9818 ball joints that were made in Japan.
FYI use a drain pan to catch the fluid when you unscrew the large nut to take out the OEM strut insert from inside the OEM strut bodies (54302-3H920 & 54303-3H920). After draining the fluid, use either suspension fork cleaner or brake parts cleaner to clean the inside of the OEM strut bodies of all residual fluid. The KYB front struts (NSC6004) are sealed assemblies, so you DO NOT replace the fluid when installing the KYB struts into the OEM strut bodies. The KYB struts come with a thick spacer that fits into the bottom perch of the KYB struts; I secured them together with electrical tape and installed them into the OEM strut bodies. In addition, the KYB struts come with a new large nut that you will use to secure/seal the new KYB struts into the OEM strut bodies.
NSG9069 (KYB SR SPECIAL REAR STRUT SHOCK ABSORBER) x2
N183D (RS-R DOWN SUSPENSION FULL SET)
56204-60U00 (Cap-Rear Shock Absorber) x2
56217-61L10 (Bush-Rear Shock Absorber) x2
55338-60U00 (Seal-Mounting, Shock Absorber) x2
56217-39U00 (Bush-Rear Shock Absorber) x2
55322-4P701 (Bracket Assy-Mounting, Shock Absorber) x2 REUSE
55323-2Y000 (Tube-Distance, Shock Absorber Mounting) x2 REUSE
55034-0P000 (Seat-Rubber, Rear Spring Upper) x2
56218-61L10 (Bush-Rear Shock Absorber) x2
55248-2Y00A (Cover-Bound Bumper, Rear) x2 REUSE
55240-0P000 (Bumper Assy-Bound, Rear Suspension) x2
55031-41L00 (Tube-Rear Spring) x2 REUSE IF POSSIBLE
The Q45's with active suspension use shock absorber bushings (56217-39U00 & 56218-61L10) that are reinforced with a metal tube insert (55323-2Y000), whereas Q45's that don't have active suspension use shock absorber bushings (56217-61L10 & 56218-61L10) that are not reinforced by a metal tube insert. There are two part numbers listed for the shock absorber bracket mount (55322-0P000 & 55322-4P701), which I was unable to tell the difference between the two. I decided to reuse my original shock absorber bracket mount (55322-4P701) with the active suspension shock absorber bushings (56217-39U00 & 56218-61L10) and reinforced metal tube insert (55323-2Y000). When I checked for the active suspension shock absorber bushings, I saw they are discontinued/NLA on infinitipartsdeal.com; however, you may be able to find them elsewhere. If not, use the shock absorber bushings for the non-active suspension Q45's and discard the metal tube insert. There are several OE shock absorber bushings options listed on rockauto.com.
Regarding the front and rear OEM actuators that sit on top of the factory active suspension shocks, I disconnected and removed all four without throwing a code or a dash light.