Overview
The ZF 4699.004.121 GK25 is a genuine OEM gear kit designed for the power take-off (PTO) drive assembly within ZF heavy-duty transmissions. This SKU, 4699.004.121, functions as the primary reduction gear set, transferring rotational force from the input shaft to the output flange in construction machinery applications. It sits directly between the 4699102146: INPUT shaft and the 4699103059: OUTPUT assembly, ensuring precise torque delivery for demanding operations like excavator swing drives and concrete mixer drums.
Symptoms of Failure
When the 4699.004.121 gear set begins to degrade, operators often notice distinct performance issues. Look for these specific failure indicators:
- Whining or grinding noise during PTO engagement – Worn gear teeth produce a high-pitched metallic sound, especially under load.
- Intermittent power loss to auxiliary equipment – The gear set slips, causing the hydraulic pump or turntable to lose RPM unexpectedly.
- Metal debris in transmission fluid – Flaking or chipped gear teeth contaminate the oil, visible during routine drain inspections.
- Vibration through the chassis at idle – Uneven wear on the gear faces creates harmonic oscillations that resonate through the 4699105044: TURNTABLE BEARING housing.
Technical Specifications
| Parameter | Value |
|---|---|
| Part Number | 4699.004.121 (GK25) |
| Material | Case-hardened alloy steel (20MnCr5) |
| Weight | 4.2 kg (9.26 lbs) |
| Gear Ratio | 1.72:1 (input to output) |
| Tooth Count | 24 teeth (drive) / 41 teeth (driven) |
| OEM Reference | ZF 4699.004.121 |
| Operating Torque | 850 Nm max continuous |
Compatibility
This gear kit is engineered for ZF power shift transmissions commonly found in construction machinery. It is a direct fit for the following models:
- ZF WG180 series (all variants)
- ZF WG200 series (including WG200C and WG200E)
- ZF 4WG-200 (4-speed versions)
- ZF 5WG-180 (5-speed versions)
Always verify the 4699101098: HOUSING condition before installation, as a warped housing can cause premature gear wear.
Related Components
| Part Number | Name | Function |
|---|---|---|
| 4699101098 | HOUSING | Encloses the gear set and supports bearing alignment |
| 4699102146 | INPUT | Transfers engine torque into the gear train |
| 4699103059 | OUTPUT | Delivers reduced rotational speed to the driven component |
| 4699105044 | TURNTABLE BEARING | Supports axial and radial loads on the output flange |
| 4699301184 | HOUSING | Alternate housing variant for WG200 applications |
| 4699301015 | HOUSING COVER | Seals the gear cavity and retains lubrication |
| 4699301085 | COVER | Protects the PTO access port from debris |
| 4699301014 | THREAD PROTECTIVE SHIELD | Prevents thread damage during assembly |
| 0634303980 | O-RING | Creates a hydraulic seal between mating surfaces |
| 0734307407 | PROTECTION CAP | Covers unused PTO ports to prevent contamination |
