Prepare and Support the Trailer Safely
- Prepare the work area and identify crush hazards.
- Separate frame support from axle support.
- Protect wiring and hoses during axle lowering.
- Appropriately rated lifting equipment — Lift the trailer at its frame using the trailer manufacturer's recommended method.
- Appropriately rated jack stands — Support the trailer frame before anyone works underneath.
- Suitable axle supports — Carry each axle's own weight while suspension connections are disconnected.
- Inspection light — Illuminate support locations, suspension connections, wiring, and hydraulic hoses.
- Safety glasses — Provide eye protection as part of the appropriate personal protective equipment.
Read the applicable installation instructions and safety labels before working. Wear appropriate personal protective equipment, including eye protection, and keep clear of moving parts that can pinch, cut, or crush.
Lift the trailer by its frame according to the trailer manufacturer's recommendations. Support the frame with appropriately rated jack stands before working underneath; the axle and suspension must not carry the trailer's weight at lifting contact points.
Additional supports under the axles serve a different purpose: they carry the axles' own weight while suspension connections are disconnected. On a multi-axle trailer, support each axle before disassembling suspension components.
Inspect electrical wiring and hydraulic hoses before lowering an axle. If their length prevents lowering, disconnect them only after switching off electrical power and de-energizing the hydraulic system. Allowing an axle to drop can damage brake wiring.
How It Works
Establish the trailer's support path
Read the applicable installation instructions and safety labels before selecting the lifting and support arrangement. Lift by the frame using the trailer manufacturer's recommended method, then support the frame on appropriately rated jack stands before working underneath. Lifting equipment alone is not safe support, and the axle or suspension must not carry the trailer's weight at lifting contact points.
Support axles independently
Frame stands carry the trailer, while separate axle supports carry the axles' own weight during suspension disassembly. Disconnecting suspension components removes restraints that normally hold an axle in position, allowing an unsupported axle to move or fall. Support each axle before disassembly and keep clear of locations where movement could pinch, cut, or crush.
Protect connected services
Inspect electrical wiring and hydraulic hoses before lowering an axle because available length can limit its travel. A falling axle can pull on wiring and damage brake connections; hoses can also be strained when movement exceeds their available slack. If disconnection is necessary, switch off electrical power and de-energize the hydraulic system before disconnecting.
Step-by-Step Procedure
0/6 doneDiagnostic Chart
| Symptom | Check | Spec / Expected | Likely cause & fix |
|---|---|---|---|
| The trailer is ready for service but remains supported only by lifting equipment. | Before anyone goes underneath, verify that appropriately rated jack stands support the frame. | Never work beneath a trailer supported only by lifting equipment or by its axle or suspension. | The lifting operation has not been followed by a safe frame-support arrangement. Basis: ccd-0011277 |
| The trailer's weight is carried through an axle or suspension lifting contact. | Compare the lifting contact locations and method with the trailer manufacturer's recommendations. | Lift the trailer by its frame; the axle and suspension must not carry the trailer's weight at lifting contact points. | The selected lifting arrangement incorrectly uses the axle or suspension to carry the trailer. Basis: ccd-0011277 |
| Suspension disassembly is about to begin with an axle unsupported. | Confirm that each axle has separate support carrying its own weight before connections are disconnected. | On a multi-axle trailer, support each axle before disassembling suspension components. | Frame support has been mistaken for support of the axle after its suspension connections are removed. Basis: ccd-0011277 |
| Wiring or hydraulic hoses restrict the intended axle-lowering movement. | Inspect available length before lowering and determine whether disconnection is necessary. | Disconnect only after switching off electrical power and de-energizing the hydraulic system. | Connected wiring or hoses lack sufficient available length for the intended movement. Basis: ccd-0011277 |
At the Bay: Diagnose the Case
CASE 1 / 4
The trailer is ready for service but remains supported only by lifting equipment.
- Test
- Compare
- Correct
Select the next check
Basis: ccd-0011277. A likely cause is a hypothesis; confirm it with the applicable service procedure before repair.
Common Bay Mistakes
- ✕ Treating lifting equipment as permanent support for under-trailer work.
- ✕ Assuming frame stands also support disconnected axles.
- ✕ Beginning suspension disassembly before each axle is supported.
- ✕ Lowering an axle without checking wiring and hose length.
Quick Check
Practice only — not scored.
Plan the Service Sequence
Planning practice only. Follow the applicable manufacturer's instructions, employer safety program and qualified supervision on real equipment.
Plan the first action. Compare the service steps with the bay mistakes.
Hands-on: Shop Test Equipment
Dial Indicator — Bearing End Play
Magnetic-base dial indicator (0.001 in) on the hub face, spindle nut adjustment
🛠 Equip your bay for this test →Symptom: Bearing service — set end play after repack.
Spec limits used
- 0.001–0.010 in — Allowable end play, double-nut wheel end (Dexter 9-15K service manual, p.64)
- 0.008 in — Nev-R-Lube 50 mm max axial end play (Dexter 059-831-00)
- illustrative only — Face runout limit (General shop practice)
Simulated readings for practice. Always follow the manufacturer's procedure and values on a real trailer.
Source: ccd-0011277 — 2-3, 6