How to Choose Between Housing, Reduction Assembly and Complete Final Drive for Excavators
2026/09/19
Published by GUANGZHOU JIAJUE MACHINERY EQUIPMENT CO.,LTD
Selection guide updated: 21 September 2026.
Choose the purchasing scope after a workshop has identified which parts can be reused. A housing-only repair is a candidate when the housing needs replacement and the retained components meet the applicable service limits. A reduction assembly becomes a candidate when the gear section needs extensive work but the hydraulic motor is acceptable. A complete final drive is worth comparing when the motor and reduction unit both need work or the rebuild scope is uneconomic.
These are conditional selection paths, not a diagnosis of a particular excavator. This guide uses our 9219274 travel gearbox listing for ZX870-5G as a real housing-photo example. Its photographs do not establish that internal gears, bearings or a hydraulic motor are included.
What is the difference between a housing, reduction assembly and complete drive?
The three descriptions refer to different supply scopes. In a hydraulic track drive, the motor and reduction mechanism work together, but a supplier can quote a casing, a gearbox assembly or a combined package. Bonfiglioli's 700CK description provides a manufacturer example of a track drive powered by an integrated hydraulic motor; it is not a compatibility reference for the 9219274 item.
| Part of the drive | Function and supply boundary | Evidence needed |
|---|---|---|
| Housing / casing | Supports and locates components; a housing-only quotation does not include a gear train or hydraulic motor unless explicitly listed. | Housing reference, flange and bore measurements, and a list of fittings included. |
| Reduction mechanism | The gear train reduces speed and transmits torque to the output. An assembly offer must state which gears, shafts, bearings and seals are fitted. | Itemised assembly contents, reduction-ratio specification and applicable inspection record. |
| Hydraulic motor | Converts hydraulic power into rotation to drive the reduction mechanism. A complete-drive offer should identify the motor as well as the gearbox. | Motor reference, configuration, connections and the exact assembled package offered. |
Conceptual arrangement: hydraulic motor → reduction gear mechanism within its housing → track-drive output. This text diagram identifies functions only. It is not an exploded drawing, and it does not show the exact internal arrangement or supplied contents of the photographed product.
Which inspection findings support each option?
| Inspection finding | Option to evaluate | What must be resolved first |
|---|---|---|
| Cracked or damaged housing; retained parts accepted for reuse | Housing replacement and rebuild by the workshop. | Cause of damage, housing fit, bearing seats, gears, shafts and seals; documented reuse limits and assembly procedure. |
| Extensive gear or bearing damage; motor separately accepted for reuse | Reduction assembly, compared with an itemised rebuild quotation. | Exact ratio and interfaces, motor condition, contamination assessment and included internal components. |
| Damage or an uneconomic repair scope involving both motor and reduction unit | A verified complete final-drive package. | Application, motor and gearbox configuration, supplied accessories, installation and commissioning requirements. |
| Weak travel, noise or leakage without a completed diagnosis | Inspection before selecting any of the three purchasing scopes. | The source of the symptom; a hydraulic, control or other machine fault can require a different repair. |
A housing crack does not prove that the internal gears and bearings are sound. Ask the workshop to record the extent and cause of damage and its reuse decisions, including the relevant measured fits or clearances. A purchasing decision needs that record even when the visible defect appears confined to the outside.
Broken gear teeth or bearing debris require a wider contamination assessment. SKF explains that particles remaining from a previous failure or gear wear can damage bearing contact surfaces. The practical procurement consequence is to include cleaning, inspection and any rejected components in the repair scope, rather than price only the visibly broken item.
How do parts cost, labour and downtime compare?
The table below describes what to price; it is not a universal low-to-high ranking. A housing may involve fewer purchased components but more rebuilding work. An assembled unit may reduce that work, yet lose its time advantage if delivery is slower or its configuration is wrong.
| Purchase scope | Parts cost to request | Repair labour to request | Downtime and delay to assess |
|---|---|---|---|
| Housing only | Housing plus every rejected internal part, seal, bearing or fitting required by the rebuild. | Strip-down, cleaning, measurement, transfer of reusable components, assembly and verification. | Inspection and rebuild capacity plus availability of every required part. Hidden damage may extend the job. |
| Reduction assembly | Assembled gearbox with an explicit component list; include retained-motor interface items separately. | Removal, motor transfer where applicable, installation and the specified checks. | Assembly lead time and workshop availability; an unverified retained motor can cause further delay. |
| Complete final drive | Motor and reduction package, accessories, freight and any required installation items. | Removal, installation and application-specific checks or setup. | A compatible available unit may reduce rebuilding work; freight and commissioning can still govern completion. |
Use the same calculation for all technically acceptable options: quoted parts + workshop labour + inspection and required fluids or clean-up + freight + attributable downtime cost. Use your workshop's estimated hours and your own verified idle-time or substitute-machine cost. Do not double-count lost production and replacement-machine costs for the same effect. No fixed price, repair-hour estimate or saving percentage is claimed here.
What can the real housing photographs help you compare?
Figure 1 records the external housing shape and flange areas. Figure 2 gives another view of the flange and central opening. Compare the old component from matching directions, then obtain the specified bore, hole-circle and flange dimensions with units and measuring references. Perspective photographs cannot supply accurate millimetre values.
The reduction gears and motor are not visible in these two photographs. Request an itemised assembly drawing or actual internal and motor photographs if those parts are included in the offer. A motor photograph from another product would not establish the contents or compatibility of this housing listing.
A selection example: why a low casing price may not settle the order
Consider an illustrative workshop assessment: the casing is cracked, one bearing is rejected, and the remaining gear train and motor still need inspection. A housing-only quotation is incomplete at that stage. First add the rejected bearing and other required items, complete the reuse assessment, and obtain the rebuilding estimate. Then compare that total with an exactly specified reduction assembly and complete-drive offer.
If the retained components pass inspection and the workshop can complete the rebuild promptly, the housing route remains a candidate. If further internal damage expands the work, reassess the assembly options. This example explains a decision process; it is not a customer case or a reported repair outcome.
Send a quotation request that allows a technical comparison
- Machine model and serial number, installed drive reference and motor identification.
- The requested scope: housing, reduction assembly or complete final drive.
- Workshop findings, components accepted or rejected for reuse, and unresolved checks.
- Matching flange, drive, connection and label photographs, plus relevant measured data.
- Required component list, quantity, condition, inspection documentation and delivery destination.
Ask each supplier to identify its exact offered reference, included components, exclusions and confirmed lead time. Keep 9219274 separate from any proposed alternative number until the application match is documented. Request a revised quotation whenever the repair scope changes.
Basis: original G-logo product photographs; Bonfiglioli 700CK product description; SKF Bearing damage and failure analysis, contamination discussion. Reviewed on 21 September 2026. Manufacturer references explain general principles and do not certify this offered product. No in-house rebuild, measured repair cost or engineer review is claimed.
Send your final-drive identification and inspection findings to GUANGZHOU JIAJUE MACHINERY EQUIPMENT CO.,LTD for a quotation with a defined supply scope.
