Overview
The ZF 4651.221.003 SUCTION TUBE is a critical fluid delivery component engineered for the WG 100 Series transmission family. This OEM genuine part, identified by SKU 4651.221.003, resides within the lower valve body and sump area, where it draws pressurized transmission fluid from the pan and directs it toward the pump inlet. By maintaining a consistent, uninterrupted flow of hydraulic oil, this suction tube ensures proper lubrication and cooling across all rotating assemblies. It works in direct conjunction with the 4651101006: TRANSMISSION HOUSING and the 4651301034: HOUSING to create a sealed, low-restriction fluid path. Without a properly functioning suction tube, the entire hydraulic circuit becomes compromised, leading to rapid wear of internal components.
Symptoms of Failure
When the ZF 4651.221.003 suction tube degrades or cracks, operators will notice distinct performance issues. Look for these specific failure indicators:
- Low fluid pressure at idle: A cracked suction tube allows air ingestion, causing the transmission to struggle building pressure when stationary. This often triggers a “low line pressure” diagnostic code.
- Intermittent gear slipping under load: As the tube loses its seal, hydraulic flow becomes erratic, leading to delayed engagement or momentary slipping during acceleration.
- Visible oil leaks around the sump area: A fractured suction tube or degraded O-ring at its mounting point will drip transmission fluid directly beneath the bell housing.
- Whining or cavitation noise: Air entering the system through a damaged tube creates a high-pitched whine from the pump, especially noticeable at cold start-up.
Technical Specifications
| Specification | Detail |
|---|---|
| Part Number (SKU) | 4651.221.003 |
| Material | Die-cast aluminum with nitrile sealing surfaces |
| Length (approx.) | 285 mm |
| Inner Diameter | 18.5 mm |
| Weight | 0.42 kg |
| OEM Reference | ZF 4651.221.003 (Genuine) |
| Sealing Method | Integrated O-ring groove (uses 0634303928: O-RING) |
Compatibility
This suction tube is precision-machined for the WG 100 Series but also fits select ZF off-highway and industrial transmissions. Compatible models include:
- ZF WG100
- ZF WG120
- ZF WG150
- ZF WG180
- ZF WG200
Installation requires careful alignment with the 4651301013: HOUSING to prevent cross-threading. Always replace the sealing O-ring (part 0634303928) during service to ensure a leak-free fit.
Related Components
| Part Number | Name | Function |
|---|---|---|
| 4651101006 | TRANSMISSION HOUSING | Main structural casing for gear sets |
| 4651301034 | HOUSING | Intermediate fluid routing chamber |
| 0634303928 | O-RING | Seals suction tube to housing |
| 4651301013 | HOUSING | Lower valve body support housing |
| 4651301015 | SCREEN SHEET | Primary fluid filtration mesh |
| 4651301035 | SCREEN SHEET | Secondary fine filtration screen |
| 0630361028 | SEALING CAP | Closes unused hydraulic ports |
| 4475280060 | SCREW PLUG | Threaded port seal for pressure tests |
| 0634303312 | O-RING | Seals screw plug to housing |
| 0630361063 | SEALING CAP | High-temp cap for cooler line ports |
