WIX Filters · 51xxx · return line
51729 filter element: specifications & equivalents
The 51729 is a WIX Filters return-line hydraulic filter element, built with microglass media, sized 121.2 × 361.7 mm OD × length, rated at 4 µm class (β2 = 4, β20 = 12). Verify against the current manufacturer data sheet before ordering.
Envelope OD × L 121.2 × 361.7 mm
Filtration rating 4 µm nom.
Beta rating β 2 = 4, β20 = 12
Media Microglass
Thread 1-3/4-12
Collapse / burst 55.158 bar
Line type return
Catalog verified. Parameters extracted from the manufacturer’s electronic
catalog / official interchange document and checked 2026-09-27. Confidence score 0.90.
Specification table
| Parameter | Value |
|---|---|
| Filter type | return line |
| Media | Microglass |
| Filtration rating | 4 µm |
| Rating basis | nominal |
| Beta ratio | β2 = 4, β20 = 12 |
| Outside diameter OD | 121.2 mm |
| Length | 361.7 mm |
| Thread / connection | 1-3/4-12 |
| End caps | spin-on baseplate with attached gasket |
| Flow direction | outside-in |
| Collapse / burst pressure | 55.158 bar |
| Integral bypass valve | none (housing/valve-dependent) |
| Seal material | Nitrile (NBR) |
| Manufacturer part no. | 51729 |
| Source catalog | WIX Filters (MANN+HUMMEL): WIX Filters online product catalog |
| Last verified | 2026-09-27 |
Sources: WIX Filters (MANN+HUMMEL) — WIX Filters online product catalog — accessed 2026-09-26.
WIX Filters® and all model designations are trademarks of their respective owners, used here for identification only — ElementRef is an independent reference site, not an authorized WIX Filters distributor.
Dimensions & series range
| Outside diameter | 121.2 mm (4.772 in) |
| Overall length | 361.7 mm (14.240 in) |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| ↔ P170949 | Donaldson | partial | Same spin-on envelope (1-3/4"-12 thread, ~121 mm OD) per Donaldson cross-reference table, but micron grade differs — Donaldson 11 µm vs WIX 4 µm nominal. Not a drop-in for cleanliness-critical circuits; confirm ISO cleanliness target before substituting. |
Interchange levels: full catalog-confirmed drop-in · partial verify parameters · verify manual confirmation required. Links resolve to the equivalent model's specification page where available.
How the 51729 model number is decoded
- 51729WIX hydraulic spin-on filter part number.
- 1-3/4-12Mounting thread: 1-3/4-12 (spin-on baseplate).
- MicroglassFilter media: Microglass.
Typical equipment & applications
- Mobile and industrial hydraulic return circuits
- Construction and agricultural equipment
- Heavy-duty transmission and torque-converter circuits
Selection pitfalls — read before you substitute
- A return-line element is not a pressure-line element: return cartridges (BN4HC low-collapse) tolerate roughly 20 bar differential, while BH4HC pressure executions are rated to 210 bar. Installing a low-collapse element in a pressure housing can rupture the media on cold-start spikes.
- This element has no integral bypass — opening pressure is set by the housing’s reusable bypass valve. Confirm the valve setting (commonly 3.4 bar) is present before fitting.
- “10 µm nominal” and “12 µm at β1000” can describe the very same media — one is reported at β≥200, the other at β≥1000 per ISO 16889. Compare ratings at the same Beta test point, not just the printed micron number.
- Nitrile (NBR) seals are standard for mineral hydraulic oil but fail early in some phosphate-ester fluids and at sustained high temperature; verify seal compound against the fluid data sheet (fluorocarbon/Viton executions may be required).
- Fine 4 µm media loads faster and runs at a higher cold Δp than coarser grades — only downgrade cleanliness targets if the system ISO 4406 code allows it.
- End-cap geometry and the number/position of O-rings block interchange even when OD and length match — visually compare end caps before fitting, especially with aftermarket cartridges.
Frequently asked questions
What are the dimensions of the 51729 filter element?
The published envelope is 121.2 mm OD × 361.7 mm length (4.772 × 14.240 in). Confirm against the housing drawing before ordering.
What micron rating does 51729 use?
This element is rated 4 µm (nominal class) — β2 = 4, β20 = 12. Always compare Beta ratings at the same test point: two brands may print different micron numbers for the same physical grade.
What replaces the 51729 filter element?
1 partial match(es) requiring parameter review
How do I read the 51729 part number?
See the designation decoder above: each segment of 51729 encodes size, line type, filtration grade and media/collapse execution.
Is a same-envelope aftermarket element always a drop-in replacement?
No. Matching OD and length only proves the cartridge fits the bowl. End-cap style, seal compound, micron/Beta rating, collapse pressure and bypass configuration must also match; the table above tags every equivalent as full, partial or verify for exactly this reason.
How often should a hydraulic return-line element be replaced?
Replace at the housing manufacturer’s recommended differential-pressure setting (commonly signalled by a clogging indicator), or on a time-based service interval when no indicator is fitted — never wait for bypass to open continuously, because unfiltered oil then reaches the valves.
Other models in the 51xxx series
All 306 →Reviewed & verified by the ElementRef engineering desk against WIX Filters (MANN+HUMMEL) on 2026-09-27. Read our editorial & correction policy.