AST ASTLS-14-1403 Rear Lowering Springs for 1984-1989 Nissan 300ZX Z31 3.0L V6

Vehicle Fitment

• 1984-1989 Nissan 300ZX (Z31, 2-Seat Coupe, 3.0L V6 VG30E Naturally Aspirated, RWD)
• 1984-1989 Nissan 300ZX Turbo (Z31, 2-Seat Coupe, 3.0L V6 VG30ET Turbocharged, RWD)
• 1984-1989 Nissan 300ZX (Z31, 2+2 Coupe, 3.0L V6 VG30E Naturally Aspirated, RWD)

Fitment Notes

• This kit contains two rear lowering springs only. It is a rear-only application - front springs are not included and are not part of this part number.
• When installing, remove the original OEM rubber isolator from the factory spring and transfer it onto the AST lowering spring in the same position. Mount the rear spring with the progressive (closely-wound) end facing upward - this orientation is critical for correct function.
• Not suitable for Z31 models equipped with factory ride-height level adjustment or electronically controlled suspension systems (GLL trim with adjustable suspension).
• Not suitable for 4WD variants. All Z31 300ZX models sold in North America and Europe were RWD only - this note applies globally per AST's standard exclusion language.
• Not suitable for station wagons or estate body styles - the Z31 was not offered in these body styles in any major market; this is a standard AST exclusion disclaimer.
• Drop amount: 35mm rear. Front drop is not applicable to this kit.
• Fitment covers the 1984-1989 model years, encompassing both Zenki (1984-1985), Chuki (1986), and Kouki (1987-1989) production variants of the Z31 chassis.

Features

• Vehicle-specific progressive spring rate, developed and tuned by AST engineers for the Z31 rear suspension geometry and chassis weight to deliver the correct drop and spring behavior.
• Lowers the rear ride height by 35mm, reducing the rear center of gravity, improving rear cornering stability, and eliminating excess wheel arch gap for a more aggressive, planted stance.
• Progressive spring design provides a meaningful improvement in rear body roll resistance and overall chassis balance without introducing excessive harshness at low speeds or over road imperfections.
• Direct OEM rear spring replacement - mounts in the factory rear spring perches using the transferred OEM rubber isolator; no modification to the rear suspension required.
• Manufactured from premium high-tensile chromium-silicon wire, individually handpicked by AST engineers for metal consistency and long-term fatigue performance.
• Cold-wound on precision Wafios coiling machines, then heat-treated to increase material hardness and eliminate residual winding stress.
• Each spring is individually shot peened, phosphate treated, and powder coated for maximum corrosion resistance and service life.
• Each spring is blocked and computer-tested prior to shipment, minimizing post-installation settling so the drop height is achieved immediately upon installation.
• Most AST spring applications are TUV certified - certificates available upon request.
• Lifetime warranty against breakage - backed by AST Suspension's manufacturer guarantee.

Specifications

• Part Number: ASTLS-14-1403
• Type: Fixed Rear Lowering Springs - rear application only
• Spring Design: Progressive rate
• Spring Material: Premium high-tensile chromium-silicon wire
• Manufacturing Process: Cold-wound, heat-treated, shot peened, phosphate treated, powder coated, computer-tested
• Rear Lowering: 35mm
• Front Lowering: Not applicable (front springs not included)
• Drivetrain: RWD only
• Fitment Style: Direct OEM rear spring replacement (OEM rubber isolator must be transferred)
• Rear Spring Orientation: Progressive end (closely-wound coils) must face upward during installation
• Warranty: Lifetime against breakage
• TUV Certification: Available upon request
• Position: Rear Left, Rear Right

Included Components

• 2x Rear lowering springs (left and right)

Product Description

The AST ASTLS-14-1403 is a rear-specific lowering spring set engineered for the 1984-1989 Nissan 300ZX Z31 in both naturally aspirated (VG30E) and turbocharged (VG30ET) configurations. Providing a 35mm rear drop, this kit is designed to correct the rear ride height, reduce the rear center of gravity, and improve the balance and cornering character of the Z31 platform. Because the Z31 uses a rear multi-link independent suspension with a distinct spring perch design, AST developed this as a rear-only application - and the drop figure is calibrated for the rear suspension geometry specifically. The progressive spring rate delivers meaningful improvements in rear body roll control without the harshness of a linearly rated spring, maintaining acceptable ride quality for street use while visibly transforming the car's stance.

Installation requires transferring the OEM rubber spring isolator from the factory spring directly onto the AST lowering spring at the same position along the coil. Critically, the rear spring must be mounted with the progressive end - the closely-wound portion of the coil - facing upward. Incorrect orientation will result in improper spring behavior and incorrect ride height. This is a confirmed AST installation requirement for this application. The Z31's 1984-1989 production run spans three distinct visual generations: the Zenki (1984-1985), Chuki (1986), and Kouki (1987-1989) models. All three generations share the same rear spring specification and are covered by this part number, regardless of whether the car is a 2-seat or 2+2 coupe body.

AST manufactures these springs from premium high-tensile chromium-silicon wire on precision Wafios coiling machines, with each spring undergoing heat treatment, shot peening, phosphate treatment, powder coating, and individual computer-load testing prior to shipping. The computer test step is particularly important - it pre-loads and blocks each spring to minimize settling after installation, so the target drop height is achieved immediately rather than gradually over the first few hundred miles of driving. Every spring is backed by AST's lifetime warranty against breakage, and TUV certification documentation is available upon request for owners who require it for track events or technical inspection.