The 4.5 V8 W108 sedans used a hydropneumatic rear compensator for self-leveling under load. The part is no-longer-available and expensive, so most cars have been converted to a cheaper coil-spring kit. …
Hydropneumatic rear-axle compensator on V8 W108s: NLA and spring-swapped
Mercedes-Benz 250S-300SEL 6.3 (W108/W109) · mechanical