QA1 RCK52446 Rear Pro-Coil MOD Series Adjustable Coilover Conversion Kit 12in. 220lb. Springs

The QA1 RCK52446 is a bolt-in rear coilover conversion kit designed for 1973–1977 GM A-Body vehicles, featuring the advanced MOD Series shock with the highest level of on-car tunability available. This complete kit replaces the factory rear suspension with a fully adjustable coilover setup, delivering a dramatic improvement in handling, ride quality, and stance control.

At the heart of this kit is QA1's multi-patent-pending MOD Series shock, engineered specifically for high-performance drag racing and pro-touring applications. The standout feature is QuickTune Technology—dry modular valve packs that can be swapped out in minutes while the shock remains on the vehicle, without interrupting the oil path or exposing the shock to debris or air contamination. Medium compression and rebound valve packs are included standard, with soft and firm packs available separately for further tuning.

The MOD Series shock also incorporates a double adjustable design with adjustable low-speed bleed, allowing fully independent control over compression and rebound characteristics. Combined with the multiple valve pack options, this creates an expansive force curve capability and an unmatched level of tunability for changing track conditions.

Kit Includes:

• 2 MOD Series aluminum coilover shocks
• 2 American-made 12-inch high-travel springs — 220 lb/in spring rate (firm ride feel)
• Specially designed USA-made mounting brackets
• All necessary mounting hardware

Key Features:

• Bolt-in installation — no cutting or welding required
• Fully threaded aluminum shock body for ride height adjustability
• QuickTune Technology for rapid on-car revalving
• Double adjustable valving with independent compression and rebound control
• Nitrogen-charged canister available in piggyback or remote configuration
• Indexable base eyelet for flexible shock and canister placement
• Lightweight high-travel springs with reduced unsprung weight for faster suspension response
• 100% dyno tested and serialized
• Rebuildable and revalveable by QA1 factory or authorized service centers
• Proudly made in Lakeville, Minnesota, USA

The 220 lb/in spring rate is suited for a firm ride feel, making this kit an excellent choice for performance street and track driving. QA1's lightweight Pro Coil springs feature fewer coils and a smaller wire diameter than standard coil springs, resulting in increased suspension travel and reduced unsprung weight for optimized handling response.