Overview
The ZF 0737.835.159 UNION SCREW is a critical hydraulic sealing component engineered specifically for the WG 200 and WG 210 series transmissions. This OEM genuine part functions as a precision-threaded connector within the transmission’s oil circulation circuit, ensuring a leak-proof seal between the hydraulic lines and the valve body assembly. By maintaining proper fluid pressure, the union screw directly supports consistent clutch engagement and torque converter operation. The SKU 0737.835.159 is machined to exact ZF tolerances, making it a direct replacement for worn or damaged factory-installed units. When paired with a robust TRANSMISSION HOUSING, this component forms the backbone of the transmission’s internal fluid routing system.
Symptoms of Failure
- Hydraulic fluid seepage at the union screw connection: Visible oil drips or wet spots around the screw head indicate a compromised seal, often leading to low fluid levels and erratic shifting.
- Delayed gear engagement or slipping under load: A worn union screw cannot maintain adequate line pressure, causing the transmission to hesitate when shifting from Neutral to Drive or Reverse.
- Audible whining or cavitation noise from the pump: Air ingress through a loose or cracked union screw creates aeration in the hydraulic fluid, producing a high-pitched whine during acceleration.
- Intermittent loss of forward or reverse gears: Severe fluid loss from a failed union screw can trigger low-pressure warnings, resulting in temporary gear disengagement.
Technical Specifications
| Parameter | Specification |
|---|---|
| Part Number (SKU) | 0737.835.159 |
| Material | Case-hardened steel with zinc-nickel plating |
| Thread Size | M18 x 1.5 (metric fine) |
| Overall Length | 42 mm |
| Hex Head Size | 22 mm (AF) |
| Weight | 0.065 kg |
| OEM Reference | ZF 0737.835.159 |
| Sealing Type | Integrated copper washer (replaceable) |
Compatibility
This union screw is engineered for ZF WG-series transmissions, with primary application in the WG 200 and WG 210 series. It is also compatible with the WG 180 series when used in conjunction with the correct TRANSMISSION HOUSING variant. The part fits both standard and high-torque versions of these models, including WG200-6 and WG210-8. For proper identification, always cross-reference the TYPE PLATE affixed to your transmission housing. Additionally, the union screw works with the GROOVED STUD that secures the valve body cover, ensuring complete hydraulic circuit integrity.
Related Components
| Part Number | Name | Function |
|---|---|---|
| 4644101216 | TRANSMISSION HOUSING | Main structural casing for gear and clutch assembly |
| 4644301223 | TRANSMISSION HOUSING | Alternate housing variant for WG210 series |
| 0730365067 | TYPE PLATE | Identification plate with transmission serial and model |
| 0631311009 | GROOVED STUD | Locating pin for valve body alignment |
| 4644303060 | COVER PLATE | Seals the hydraulic control unit access port |
| 4644303061 | COVER PLATE | Reinforced cover plate for high-pressure circuits |
| 0634306525 | O-RING | Static seal for housing and cover interfaces |
| 0636305026 | SCREW PLUG | Drain or test port plug for hydraulic system |
| 4644301279 | SCREEN SHEET | Fine mesh filter protecting valve body from debris |
| 4644301088 | SEALING CAP | Protective cap for unused hydraulic ports |
