Take leaf springs for tool steel, coil springs for small springs and points, belts for drives and straps, sealed bearings for pulleys and wheels, and transmission and differential gears for changing speed and torque. Support the vehicle first, treat any coil spring still seated on a strut as compressed and dangerous without a spring compressor, and clamp a leaf-spring pack before its centre bolt comes out.
The mechanical parts of a car are precision components that would take a machine shop to make: springs of heat-treated steel, bearings with hardened races and gears cut to fit. Salvage turns them into the working parts of other machines.
Spring Steel, Bearings And Gears Are The Parts Hardest To Make
Leaf springs. Flat steel strips, heat-treated and tempered, found on truck and SUV rear axles. Uses (parent article): knife and tool blanks (high-carbon steel, ideal for forging), trap springs, vehicle suspension repair, and clamps and flat springs for mechanisms. See Heat Treatment for working hardened steel.
Coil springs. High-quality spring steel wound in a helix. Uses: arrow and bolt points cut into sections and ground to shape, gate and door springs, trigger mechanisms for traps and small springs for repairs.
Serpentine and V-belts. Rubber belts that drive the alternator, water pump, power steering pump and air-conditioning compressor. Uses: replacement belts for any belt-driven system, flat gasket material, durable straps, hinges and tie-downs.
Bearings. Wheel, alternator, transmission and compressor bearings, in sealed ball or roller forms. Uses: wheels for carts and wagons, low-friction pivots for wind turbines and water wheels, replacement bearings for rotating equipment, and pulleys made from a bearing, a plate and a bolt. See Roller Bearings.
Gears and differentials. Precision-cut gears and shafts in the transmission and differential. Uses: speed and torque conversion in machinery such as mills and lathes, winch mechanisms and small gears for timers.
What You Need
- Jack stands, cribbing and wheel chocks.
- A spring compressor for coil springs on struts.
- Clamps or a ratchet strap for leaf-spring packs.
- Penetrating oil, wrenches, a bearing puller or a drift and hammer.
- Gloves and eye protection.
Method: Support, Release, Remove, Inspect
Step 1: Support the vehicle so the axle and springs carry no load, using stands under the frame.
Step 2: Leaf springs. Support the axle, loosen the U-bolts and shackles with penetrating oil, and clamp the spring pack together before removing the centre bolt. Leaf springs are safer to remove than coil springs but still hold tension (parent article).
Step 3: Coil springs. Compress with a proper spring compressor before releasing the retaining nut. A spring that is already out of the car and loose is not under load.
Step 4: Belts. Release the tensioner and slip the belt off. Check for cracks and glazing.
Step 5: Bearings. Spin the bearing by hand: it should turn smoothly and quietly. Roughness, grit or play means reject it. Press or drift out wheel bearings squarely so as not to damage the race.
Step 6: Gears. Drain the oil, remove the housing and inspect teeth for chipping and wear before extracting.
Step 7: Label each part with its size and origin.
Worked Example
Gears change speed and torque in opposite directions. A 12-tooth gear driving a 36-tooth gear gives a ratio of 36 ÷ 12 = 3. An input of 300 RPM becomes 300 ÷ 3 = 100 RPM at the output, and the output torque is about three times the input torque, less friction losses. The numbers are an example; count the teeth on your own gears.
Common Mistakes
- Loosening the retaining nut on a seated coil spring. The spring releases with violence.
- Pulling a leaf-spring centre bolt with the pack unclamped. The leaves spread and fly.
- Reusing noisy bearings. They fail early under load.
- Cutting a spring with a torch. Heat ruins the temper and can throw hot fragments.
Safety
Compressed springs can kill
Vehicle suspension springs are under extreme compression and store enough energy to kill (parent article). Never cut or remove a coil spring without a spring compressor tool, and keep body parts clear of the release path. Never work under a vehicle supported only by a jack. Wear eye protection when driving out bearings or pins, since hardened parts can chip.
What’s Next
- Learn next: Mechanical Hazards — springs, airbags and pressurised systems
- Combine with: Heat Treatment — turning spring steel into tools