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Why WK2 Rear Air Springs Fail — and What This Kit Fixes

If your 2011–2016 Jeep Grand Cherokee Overland or SRT8 sits low in the rear after an overnight park, the rear air springs are the usual suspect. On the WK2 platform they are the most common Quadra-Lift® wear item past 80,000 miles.

The 2X Rear Air Suspension Spring for Jeep Grand Cherokee Overland SRT8 (2011–2016) is a precision-engineered aftermarket pair built to match or exceed OEM specifications — one left spring and one right spring in the same box.

The technology is not going anywhere: Jeep, a Stellantis N.V. brand, still deploys Quadra-Lift® on current Grand Cherokee trims including Overland®, Summit®, and Trailhawk® 4xe. Air-spring service knowledge stays useful across model generations.

Fitment and OEM Cross-Reference Numbers

• Rear-left (driver side): OEM 68029911AB
• Rear-right (passenger side): OEM 68029912AC / 68029912AD / 68029912AE / 68029912AF — all four revisions are superseded by this kit
• Aftermarket equivalents: 177C-15-R and AS-7062
• Vehicle coverage: 2011–2016 Jeep Grand Cherokee WK2, Overland and SRT8 trims with factory Quadra-Lift® air suspension
• Before ordering: verify RPO code SER — SRT8 models with factory rear Quadra-Lift® accept these springs directly

The two sides are not interchangeable. Rear-left and rear-right springs differ in airline routing and in upper mounting clocking positions, so a swap is physically not an option. The kit ships one of each side, clearly marked, which settles the left/right question before the springs leave the box.

How the Bladder Is Built

Factory WK2 rear springs use a single-layer EPDM/CR blend, and their number-one failure mode is cold-weather micro-cracking at the bellows fold line. Below roughly 5°C (41°F), the stiffened bladder opens those micro-cracks just enough to bleed pressure across a 6–8 hour cold-soak. The compressor then runs hard on every cold start, which is why the symptom gets blamed on the compressor so often.

The Koeep 2X kit replaces that single-layer design with a tri-layer vulcanized bladder:

• Inner liner: oil-resistant nitrile-butadiene rubber (NBR) that withstands compressor oil mist migration. Meets ASTM D471 oil-immersion resistance — IRM 903 oil, 70 hours at 100°C, volume swell under 10%.
• Structural mid-layer: high-density EPDM cross-linked with aramid fiber cord. Burst-strength margins above 3.5 MPa, well over the Quadra-Lift® peak operating pressure of 1.6–1.8 MPa. Exceeds ISO 188:2023 accelerated hot-air aging — 168 hours at 125°C, tensile retention above 80%.
• Outer jacket: ozone- and UV-resistant neoprene per SAE J200 Type/Class designations for underbody exposure. Passes ASTM D1171 ozone resistance — 70 hours at 50 pphm and 40°C, no cracking.

The bottom line: the tri-layer build targets the #1 WK2 rear-spring failure mode directly. With an operating envelope of −40°C to +100°C — Continental HiTemp-class thermal resilience — the cold-weather leak path that deflates your rear axle overnight is gone at the source.

For perspective: original equipment is rated from −30°C to +85°C. The Koeep bladder runs from −40°C to +100°C. That colder floor is the difference between a bladder that stiffens and cracks near freezing and one that stays elastic through a real winter.

Spec Comparison: OEM vs. Koeep 2X Kit

The Four Trouble Codes Behind a Sagging Rear End

When a rear air spring leaks, the Air Suspension Control Module (ASCM) logs a specific set of diagnostic trouble codes. All four live inside the SAE J1939-73 DM1 message structure, SPN range 520700–520799, FMI 0–31. If your scan tool shows any of them, test the rear springs before you spend money on a compressor.

• C1556-96 — Ride Height Air Pressure Sensor 1, Component Internal Failure. Commonly triggered by rear spring leakage causing sensor reading drift.
• C151E-15 — Rear Axle Height Sensor Correlation Fault, Circuit Short to Battery or Open. Often precipitated by a collapsed spring altering linkage geometry.
• C15A1-00 — Unable to Obtain Desired Ride Height, General System Performance. Sets when the rear springs cannot hold target pressure within the ASCM's 30-second timeout window.
• C1562-98 — Ride Height Air Pump Control, Component or System Over Temperature. A secondary code: a leaking spring forces continuous compressor duty cycling until the pump overheats.

Do Not Skip the Recalibration

New springs alone do not finish the repair. After installation, run a full ASCM ride-height recalibration with a J2534 pass-through device — wiTECH 2.0 or AutoEnginuity. The routine cycles each corner through all five Quadra-Lift® height presets (Entry/Exit, Aero, Normal, Off-Road 1, Off-Road 2), resets stored height offsets, and clears the adaptive memory tables.

This procedure follows Stellantis TSB 17-002-24 REV. B (2026 update). Skip it, and the module keeps comparing live height readings against stale adaptive offsets — a classic source of persistent C151E-15 correlation faults after otherwise correct hardware work.

Complete the Job: Related WK2 Suspension Parts

A failed pair of rear springs at 80,000-plus miles is a strong hint the other corners have lived the same life. For single-corner replacement or a spare, the Rear Air Suspension Spring for Jeep Grand Cherokee WK2 Overland SRT8 (2011–2016) covers one side at a time to match this part.

If your fault history also points at the front axle — harsh damping, ride-height faults under load — the 4PC Front + Rear Air Suspension Shock kit for Jeep Grand Cherokee WK2 (2011–2016) refreshes all four corners in a single job instead of four separate visits.

Both parts sit in the Steering & Suspension parts collection alongside control arms, tie rods, and bushings for this platform. Air-spring work rarely travels alone on a high-mileage Jeep, so it pays to price the whole front end while it is on the lift. And if you service the 2011–2014 Dodge Durango or Jeep Cherokee as well, our Aluminum Radiator CU13200 cooling guide covers the next aging system on those SUVs.

Order the 2X Rear Air Spring Kit

Need fleet pricing or a fitment check first? Submit the request-for-quote form, email support@koeep.com, or message the team on WhatsApp for a fast answer.

Frequently Asked Questions