Donaldson · Duramax HMK · return line

P173943 filter element: specifications & equivalents

Q: What micron rating does P173943 use?

This element is rated 150 µm absolute — not separately rated (wire mesh). Always compare Beta ratings at the same test point: two brands may print different micron numbers for the same physical grade.

The P173943 is a Donaldson return-line hydraulic filter element, built with wire mesh media, rated at 150 µm absolute (not separately rated (wire mesh)). Verify against the current manufacturer data sheet before ordering.

Filtration rating 150 µm abs.

Beta rating not separately rated (wire mesh)

Media Wire Mesh

Thread 1-3/4"-12 UNF-2B

Line type return

Partially verified. Fit and grade trace to an official interchange document; dimensional values are compiled from 0 aftermarket listing(s) and must be confirmed against the manufacturer housing drawing. Confidence score 0.85.

Element length (L) and thread are taken from the HMK housing component table. Canister OD is not printed on this catalog page and is pending extraction from the element dimension table; verify against the current Donaldson data sheet before ordering.

Specification table

Parameter	Value
Filter type	return line
Media	Wire Mesh
Filtration rating	150 µm
Rating basis	absolute
Beta ratio	not separately rated (wire mesh)
Length	294 mm
Thread / connection	1-3/4"-12 UNF-2B
End caps	spin-on baseplate with attached gasket
Flow direction	outside-in
Rated flow	189 L/min
Integral bypass valve	none (housing/valve-dependent)
Seal material	Nitrile (NBR)
Operating temperature	-29 to 107 °C
Manufacturer part no.	P173943
Source catalog	Donaldson Company: Donaldson Hydraulic Filters eCatalog
Last verified	2026-09-28

Sources: Donaldson Company — Donaldson Hydraulic Filters eCatalog — accessed 2026-09-26.

Donaldson® and all model designations are trademarks of their respective owners, used here for identification only — ElementRef is an independent reference site, not an authorized Donaldson distributor.

Cross references & equivalents

Equivalent model	Brand	Match level	Note
↔ A421T125	Filtrec	partial	Filtrec's official Cross Navigator maps DONALDSON P173943 to FILTREC A421T125 as a direct replacement, publishing the FILTREC element's OD/ID/height envelope and media grade. Rated micron differs (150 vs 125 µm) — verify efficiency class and collapse/seal for the housing 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.

Full chart: Donaldson cross reference chart →

How the P173943 model number is decoded

P173943Donaldson Duramax HMK05/25 spin-on filter part number.
1-3/4"-12 UNF-2BBaseplate mounting thread (HMK05/25 housing family).
150 µmMedia grade: 150 µm, not separately rated (wire mesh).
Nitrile (NBR)Seal material: Nitrile (NBR).

Typical equipment & applications

Case drains and lube oil systems
Cooling circuits and power transmissions
Return lines and side-loop systems

Selection pitfalls — read before you substitute

Line type is not interchangeable: return-line cartridges are low-collapse executions that typically tolerate roughly 10–20 bar differential, while pressure-line elements are commonly rated 100–210 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.
This execution uses nitrile (nbr) seals — verify the compound against the fluid data sheet: standard nitrile (NBR) can fail early in phosphate-ester fluids and at sustained high temperature, where fluorocarbon/Viton executions may be required.
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 micron rating does P173943 use?

This element is rated 150 µm absolute — not separately rated (wire mesh). Always compare Beta ratings at the same test point: two brands may print different micron numbers for the same physical grade.

What replaces the P173943 filter element?

1 partial match(es) requiring parameter review

How do I read the P173943 part number?

See the designation decoder above: each segment of P173943 encodes size, line type, filtration grade and media/collapse execution.

How often should a hydraulic filter 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 Duramax HMK series

All 40 →

P163324 23 µm P163419 23 µm P164375 7 µm P164378 11 µm P164381 11 µm P164384 33 µm P165332 7 µm P165335 50 µm P165338 50 µm P165354 33 µm

Reviewed & verified by the ElementRef engineering desk against Donaldson Company on 2026-09-28. Read our editorial & correction policy.