1937-39 Chevy Car Bolt-On Parallel Rear Leaf Spring Kit - Chassis Engineering

The 1937–1939 Chevy Car Bolt-On Parallel Rear Leaf Spring Kit (AS-1018CG) by Chassis Engineering converts classic Chevrolet passenger cars to a modern, parallel leaf spring suspension. Engineered as a direct bolt-on system, this kit replaces outdated factory rear setups and open-driveline conversions with smooth-riding 2-1/2" slider springs and matched gas shocks.

Accommodating axle housing tube diameters up to 3", this kit is compatible with popular modern rear axle swaps (such as Ford 8-inch, Ford 9-inch, and GM 10/12-bolt axles) and is designed around a recommended 58" rear track width.

Key Features & Design Highlights

• Vehicle-Specific Bolt-On Frame Brackets: Uses factory frame alignment points for 1937–1938 models, with specific placement guidance (47-1/2" measurement) for 1939 frames.

• 2-1/2" Rear Slider Leaf Springs: Features wide, smooth-riding parallel slider springs with high-vibration-absorbing rubber bushings for improved ride quality and reduced road noise.

• Adjustable Upper Shock Crossbar: Transverse upper shock bar mounts cleanly between frame rails, allowing proper clearance below the floor pan.

• Reversible Lower Shock Plates: Multi-angle lower plates can be oriented with the shock stud angled up (standard ride height) or down (lowered stance/lowrider applications).

• Gas-Charged Damping: Paired with matched gas shock absorbers to control body roll and suspension movement under load.

Technical Specification Matrix

Step-by-Step Installation Summary

1. Teardown & Front Mount Positioning: Remove factory rear end, leaf springs, shocks, and rivets. Clamp new front mounts to the frame, using line-up holes. Temporarily bolt the axle and wheels/tires to visually confirm tire centering in the fender opening before final drilling.

2. Rear Mount Installation:

   • 1937–1938 Models: Align using factory rivet holes, drill out to 3/8", and bolt in place.

   • 1939 Models: Measure back 47-1/2" from the front mount center to establish the rear mount location.

3. Spring & Shackle Hang: Bolt front leaf spring eyes using factory-style rubber bushings, insert rear shackles, align suspension geometry, and complete final frame drilling for all mounting bolts.

4. Upper Shock Crossbar Mounting: Position the upper shock tube between frame rails (approx. 38" reference measurement). Ensure the floor pan does not contact the bar to prevent cabin rattles, then drill 3/8" frame holes and bolt secure.

5. Axle Mounting & Lower Plates: Set the rear axle housing over the spring center pin. Install U-bolts, spring pads (using the center bolt spacer for GM/Nova axles or removing if unneeded), lower shock plates with studs facing inward/forward, and gas shocks.

6. Final Inspection & Clearance Checks: Verify all fasteners are torqued. Ensure suspension travel bottoms out on frame/axle snubbers and not inside the shock absorbers to prevent shock failure.

🛠️ Important Tech & Break-In Notes:

• Spring Settling: New leaf springs will naturally drop up to 1" during the first 500 miles of use. Depending on total vehicle weight, springs sitting flat or slightly reversed under load is normal operation.

• Rubber vs. Hard Bushings: Rubber bushings are specifically required to absorb road vibrations, reduce harmonic noise, and allow necessary torsional flex during suspension travel. Hard polyurethane or solid bushings are not recommended.

• Frame Protection: Always install adjustable rubber frame snubbers/bump stops so bottoming-out forces hit the rubber stops rather than over-compressing the shock absorbers.