Overview
The ZF 4644.221.002 SUCTION TUBE is a critical fluid delivery component engineered specifically for the WG180 and WG200 series transmissions. This OEM genuine part ensures a consistent, uninterrupted flow of hydraulic oil from the transmission sump to the pump inlet. Positioned within the lower valve body or pump housing assembly, the suction tube prevents cavitation by maintaining positive fluid pressure at the pump. The SKU 4644.221.002 is precision-machined to exact OEM tolerances, guaranteeing a leak-free seal and optimal lubrication for internal planetary gear sets. When paired with a properly sealed TRANSMISSION HOUSING, this tube forms the backbone of the transmission’s hydraulic circuit.
Symptoms of Failure
When the ZF 4644.221.002 suction tube begins to degrade, operators often notice these specific failure indicators:
- Intermittent gear slipping under load: A cracked or porous tube allows air ingestion, causing hydraulic pressure drops that lead to clutch pack slippage during heavy hauling.
- Whining or cavitation noise from the pump: Air entering the system through a compromised suction tube creates a distinct high-pitched whine, especially at cold start or high RPM.
- Low transmission fluid level without external leaks: Internal cracks can allow fluid to bypass the pump, leading to sump starvation and eventual overheating.
- Erratic shift timing: Fluctuating oil volume due to a failing tube disrupts the governor pressure, causing harsh or delayed shifts.
Technical Specifications
| Specification | Detail |
|---|---|
| OEM Part Number | 4644.221.002 |
| Material | Die-cast aluminum alloy (A380) |
| Length (overall) | 185 mm |
| Inlet Diameter | 32 mm (OD) |
| Outlet Diameter | 28 mm (OD) |
| Weight | 0.34 kg |
| Sealing Surface Finish | Ra 0.8 µm |
| Operating Pressure Range | 0.5 – 2.0 bar (suction side) |
Compatibility
This ZF 4644.221.002 suction tube is designed for the following ZF transmission models:
- WG 180 Series (all variants including WG180, WG180-1, WG180-2)
- WG 200 Series (all variants including WG200, WG200-1, WG200-2)
It is a direct replacement for the original equipment tube found in these heavy-duty off-highway transmissions. For proper installation, ensure the mating TRANSMISSION HOUSING is free of debris and that the TYPE PLATE is referenced for exact model identification. The tube is secured using a GROOVED STUD to prevent vibration loosening.
Related Components
| Part Number | Name | Function |
|---|---|---|
| 4644101043 | TRANSMISSION HOUSING | Main structural casing for gear and valve assembly |
| 4644301194 | TRANSMISSION HOUSING | Alternate housing variant for WG200 series |
| 0730365067 | TYPE PLATE | Identification plate for transmission model verification |
| 0631311009 | GROOVED STUD | Fastener for securing suction tube to housing |
| 4644303060 | COVER PLATE | Seals the pump access port on the housing |
| 4644303061 | COVER PLATE | Alternate cover plate for different housing configurations |
| 0634801098 | SEALING RING | O-ring for suction tube-to-housing interface |
| 0634801250 | SEALING RING | Alternate O-ring for high-temperature applications |
| 0636305026 | SCREW PLUG | Plug for test port on the suction circuit |
| 0636305019 | SCREW PLUG | Alternate plug for drain or pressure tap ports |
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