How to Replace the Rear Lower Control Arm on a Mercedes W123 & W126

Replacing the lower rear A trailing arm is a beast of a job. Here is a loooong video with the whole process. Video Chapters [00:01] Introduction: Addressing rust-through for state inspection. [00:54] Scope of Work: The extensive disassembly required. [01:57] The Brake Cable Dilemma: Why the emergency brake must be loosened. [03:15] Interior Disassembly: Removing the rear seat and backrest. [06:58] Accessing the Upper Shock Mount: Locating the cover under the seat. [08:10] Measurement Tip: Recording suspension height for proper bushing torque. [10:01] Exterior Prep: Loosening exhaust, half-shafts, and brake calipers. [12:21] The "Van Trick": Removing a stubborn rusted exhaust with a tow strap. [13:50] Hardware Details: Identifying the 16-point spline axle bolts. [19:49] Suspension Links: Disconnecting the stabilizer (anti-sway) bar. [22:42] Removing the Rotor and Caliper. [26:58] Spring Compression: Using a specialized internal spring compressor. [31:33] Emergency Brake Service: Removing springs and cables from the hub. [36:18] Lowering the Subframe: Gaining clearance for the trailing arm bolts. [39:50] Reinstallation: Mounting the new arm and compressing the spring. [44:46] Upper Shock Finishing: Installing the rod, washers, and lock nuts. [50:24] Closing Advice: Managing rusted hardware and "faint of heart" tasks. Video Summary Ralf tackles a "Roy pain in the neck" job [01:57] to save his W126 from being condemned by inspectors. The replacement of a trailing arm is a high-effort task that requires dismantling nearly the entire rear suspension and even parts of the interior. Key Technical Highlights: Interior Access: To reach the upper shock mounting nuts, the rear seat and backrest must be completely removed [03:15]. Ralf shows the hidden cover that allows access to the threaded shock rod [07:06]. Bushing Torque Secret: Before lifting the car, Ralf measures the distance from the fender to the wheel [08:10]. This is critical because suspension bushings must be tightened only when the car is at its natural ride height; tightening them while the suspension is hanging can pre-twist and ruin the new rubber [08:59]. Dealing with Rust: Ralf shares an unconventional "van trick" for a rusted exhaust, using a tow strap and another vehicle to slowly pull the pipes apart [14:43]. He also emphasizes using plenty of penetrating oil (WD-40) on the 16-point spline bolts that secure the half-shafts to the differential [13:54]. The "Magic" Tool: Removing the rear springs on a Mercedes requires a specific internal spring compressor [27:11]. Ralf demonstrates how to thread the plates into the coils to safely collapse the spring within the control arm pocket [30:20]. Subframe Clearance: A significant hurdle is that the trailing arm mounting bolts often cannot be removed without lowering the rear subframe slightly [36:28]. Ralf explains how to support the differential and subframe with a jack to gain the necessary clearance [37:21]. The Result: Despite the difficulty and "dirty" nature of the job, Ralf successfully restores the structural integrity of the rear suspension, ensuring the W126 is safe for daily driving [51:26]. Video URL:    • How to Replace the Rear Lower Control Arm ...