The Bilstein 25-325096 is a rear damper from the B8 5160 line, a 46mm monotube shock paired with a remote reservoir that carries extra shock oil away from the main body. Owners describe the 5160 as basically a 5100 with a remote reservoir. The damping platform is familiar, and the reservoir is the real change. For a lifted or heavily loaded 4Runner or GX460 built for trail use, that setup earns its price over stock units. Shop this for a 5th gen 4Runner rear remote reservoir shock, a GX460 B8 5160 monotube upgrade, or a 46mm rear reservoir shock for off-road heat dissipation.
Owners who have fitted 5160s report a practical gain. Because the reservoir takes components out of the main tube, one owner write-up describes about 1.0" of extra travel just by installing the new shocks on a solid-axle rear. Fitment is the caveat: published year ranges for the GX460 and 4Runner differ from source to source, so confirm compatibility against your VIN with the manufacturer before ordering. Check the side and quantity on your order as well, since listings do not agree on those details either.
Owners on user forums report that the shocks come with the hardware needed to mount the reservoirs to the frame, so no separate bracket purchase is typically required for a basic install.
Per the manufacturer's install instructions as quoted by owners on user forums, the hose fitting should be oriented toward the rear of the vehicle. Owners also recommend checking hose clearance against the frame through full suspension flex.
Experiences on user forums vary. One 2011 GX460 owner reported roughly 15,000 miles with no leaks, while other owners have posted leak concerns, so inspect the fittings after installation and again after your first few drives.
This is a bolt-in rear job on the stock shock mounting points, but the remote reservoir adds routing and clearance steps. Owners on user forums describe compressing the shock with a tie-down strap, threading the top mount on just enough to hold it, then seating the lower eye with a dead-blow hammer after cleaning it and applying a light coat of anti-seize. Route the hose behind the main shock tube, then tighten the reservoir clamps evenly. Before final torque, twist the body slightly outward so the hose fitting clears the frame during flex. Verify the reservoir fitting orientation against the manufacturer's install sheet, and use a floor jack and jack stands rated for the load.
