Unless your rear suspension hydraulic rams are physically damaged or leaking, it’s not likely they need to be replaced.
AHC “shocks” are hydraulic cylinders and have an extremely long life expectancy… unlike traditional shock absorbers, Active Height Control (AHC) system uses electronically controlled valuing actuators to vary the hydraulic fluid flow into and out of the “ shocks”. You can even lower for loading, have a neutral position for normal driving, and a high setting for increased ground clearance during off-roading. All by the touch of a button.
Now, the bushings in the rear control arms are a different story… Toyota does not offer these bushings for sale separately. You can purchase aftermarket bushings and press them in, or replace all four rear control arms. The OEM Toyota bushings are of a much higher quality rubber with proper durometer rating.
Replacing the globes is definitely on the top of the list in order to restore a factory fresh ride quality. Globes are nitrogen charged, and the nitrogen pressure will diminish with age… There’s no way around that. Replacing the globes will give you fresh suspension quality.
In order to provide insight and how to get the most bang for the buck, you should read through this thread, and there are many others like it on this forum.
I initially put this in the
Definitive list of AHC maintenance items thread, but at almost 800 posts long and growing, it's going to get buried and the thread itself is very unwieldy.
In an attempt to make as focused a summary as possible,
I present "The ABCs of AHC." It's intended as a comprehensive, linear checklist for anyone who needs to get their AHC back into factory tune. Information gathered from as many sources as I could find on this forum; I take no credit for developing any of this, just bringing it all together as much as possible. Special shout outs to...