Hydro-Gear Oil & Filter Guide: 52114, 72750 and What Oil to Use
Short version: Hydro-Gear's service manuals call for 20W-50 engine oil (minimum 9.0 cSt at 230 F / 110 C, API SL). The ZT-2800 through ZT-3800 and the G700 use the 52114 spin-on filter; the ZT-4400 uses 72537 and the ZT-5400 uses 71943. Hydro-Gear's oil service kits are 72750 (ZT-2800 to ZT-3800) and 72881 (ZT-4400 and ZT-5400). The EZT (ZT-2200) and T2 are factory filled and sealed, with internal filters and no routine oil change. After any oil change, purge the air out.
What oil Hydro-Gear specifies
- 20W-50 engine oil. Every current Hydro-Gear ZT, G700 and T2 service manual says: "A 20W50 engine oil has been selected for use by the factory and is recommended for normal operating procedures."
- Minimum spec: engine oil rated at least 9.0 cSt (55 SUS) at 230 F (110 C), API classification SL.
- Biodegradable oil is not approved for the ZT-4400 and ZT-5400.
- Pumps (P Series and BDP) are less specific: engine oil of at least 55 SUS (9.0 cSt) at 230 F, API SJ/CD, following the vehicle manufacturer's recommendation.
- Hydro-Gear Commercial Transaxle Oil is the oil packed in Hydro-Gear's service kits. Hydro-Gear describes it as "formulated from high-quality base stocks combined with modern performance additives." The Hydro-Gear pages we checked don't state its viscosity grade, and the manuals still specify 20W-50.
Hydro-Gear's own FAQ doesn't name an oil; it sends owners to the service and repair manuals, which is where the figures on this page come from.
Filter, oil capacity and change interval by series
| Series | Filter | Oil capacity per unit | First change | Then every | Hydro-Gear oil kit |
|---|---|---|---|---|---|
| EZT (ZT-2200) | Internal mesh filter, no service part number | 56 fl oz / 1.75 qt (1650 ml); ZT-2100: 54 fl oz (1597 ml) | Factory filled and sealed: no routine oil change. Change only if the oil is contaminated or degraded. | None listed | |
| ZT-2800, ZT-3100, ZT-3200 | 52114 spin-on | 70.3 or 71.9 fl oz (2079 or 2126 ml); 56.6 fl oz (1674 ml) with internal expansion tank. About 2 qt per unit in practice. | 75–100 hours | 400 hours | 72750 |
| ZT-3400, ZT-3600, ZT-3800 | 52114 spin-on | 71.9 fl oz (2126 ml); 56.6 fl oz (1674 ml) with internal expansion tank | 75–100 hours | 400 hours | 72750 (see note) |
| ZT-4400 | 72537 | 117–120 fl oz (3450–3550 ml) | 100 hours | 400 hours or yearly, whichever comes first | 72881 |
| ZT-5400 | 71943 | 164.8–166.5 fl oz (4875–4925 ml) | 100 hours | 400 hours or yearly, whichever comes first | 72881 |
| G700 | 52114 spin-on | 92.9–96.3 fl oz (vertical input) or 113.2–116.6 fl oz (horizontal input) | 75–100 hours | 400 hours | None listed |
| T2 / T2-HP | Internal, replaced only during internal repair | About 65–70 fl oz, depending on housing | Factory filled and sealed: no oil maintenance. An oil change means removing the transaxle from the mower. | None listed | |
Capacities exclude the external expansion tank and hoses. On the ZT-2800 family the exact volume depends on the 7th and 13th characters of the model number; a T as the 13th character means an internal expansion tank. Note on 72750: Hydro-Gear's oil page lists it as "ZT-2800 to ZT-3800" in its heading and "ZT-2800 thru ZT-3600" in its buying section, so if you have a ZT-3800, confirm with us first.
The 72750 and 72881 oil service kits
| Kit | What's in it | Fits (per Hydro-Gear) |
|---|---|---|
| 72750 Commercial Transaxle Oil Service Kit | 5 quarts Genuine Hydro-Gear Commercial Transaxle Oil, 2 Genuine Hydro-Gear Commercial filters, a fitting and a pump | ZT-2800 to ZT-3800 (ZT-3600 in one place on Hydro-Gear's page) |
| 72881 Commercial Transaxle Oil Service Kit | 10 quarts Genuine Hydro-Gear Commercial Transaxle Oil, 2 Genuine Hydro-Gear Commercial filters, filter cover O-rings | ZT-4400 and ZT-5400 |
Each kit includes two filters, one for each transaxle on a zero-turn. See what we carry in Hydro-Gear oil, filters and service kits.
The 52114 filter
The 52114 is Hydro-Gear's spin-on filter for the ZT-2800, ZT-3100, ZT-3200, ZT-3400, ZT-3600, ZT-3800 and G700. Hydro-Gear rates it at 25 micron nominal / 40 micron absolute (suction filter). The ZT-3400 manual calls for "52114 or equivalent."
52114 cross-reference (aftermarket, not Hydro-Gear)
Hydro-Gear doesn't publish a cross-reference list for the 52114; its Cross Reference Guide maps model prefixes to series, not filters. The numbers below come from an aftermarket retailer's listing for the Stens TF738 (120-738) transmission filter, which the retailer says replaces all of them. Treat it as a starting point and confirm against your mower's parts list.
| Brand | Number listed as replaced |
|---|---|
| Hydro-Gear | 52114 / HG52114 |
| Exmark and Toro | 109-3321 |
| Hustler | 600976, 768341 |
| John Deere | MIU13018 |
| Husqvarna | 539113466 |
| Ferris and Snapper | 5101026X1 |
| Ariens / Gravely | 21545100 |
| Scag | HG52114 |
| Bad Boy | 063-1050-00 |
| Dixie Chopper | 901153 |
| Country Clipper | H-2567 |
| Bush Hog | 50052929 |
| Encore | 853157 |
| Laser | 98003 |
The same listing gives the filter as 25 micron, 3/4"-16 thread, 3 in tall, with a 12–16 psi relief valve.
Changing the oil and filter (ZT-2800 through ZT-3800)
- Let it cool. On units with an internal expansion tank, drain only when the oil is below 100 F. Draining hot can lead to overfill and damage the breather.
- Drain through the filter port. The manual describes draining through the filter port, not a separate drain plug. Use a drain pan at least 12 in across; an 8-quart pan is ideal.
- Remove the filter with a socket-style filter wrench, not a strap wrench.
- Install the new filter hand tight, then turn it another 3/4 to 1 full turn after the gasket contacts the base. The ZT-3400/3600/3800 manual gives 110–130 lb-in.
- Fill: roughly 2 qt per transaxle (4 qt for a pair). Fill until oil appears at the top port, then top up through the expansion tank to the "Full Cold" line.
- Purge the air (below) and recheck the level.
ZT-4400: the manual says to apply the bypass before an oil change. ZT-4400 and ZT-5400: first change at 100 hours, then every 400 hours or yearly.
EZT (ZT-2200): only units with E or F as the 3rd character of the model number (ZC-E…, ZC-F…) have a drain plug; drain below 100 F because the internal expansion cavity can lead to overfill. The correct level is 0.75–1.50 in (19–38 mm) below the top of the fill port, checked at 50–100 F; recheck after about a minute of running. More in our EZT guide.
Purge after every oil change
Air left in the system makes a transaxle noisy, weak after a short run and hot. Hydro-Gear's procedure, in brief:
- Check the oil level and release the parking brake. Ideally, raise the drive wheels off the ground.
- With the bypass open and the engine running, slowly move the controls forward and reverse 5–6 times.
- With the bypass closed and the engine running, do the same 5–6 times. Stop the engine, check the oil and top up.
- Repeat as needed until the unit runs at normal noise and moves smoothly at normal speed in both directions.
Full steps and bypass details: how to purge a Hydro-Gear transaxle.
Frequently asked questions
What kind of oil goes in a Hydro-Gear transmission?
Hydro-Gear's service manuals specify 20W-50 engine oil with a minimum rating of 9.0 cSt at 230 F (110 C) and API classification SL. Pumps follow the vehicle maker's recommendation within a similar minimum spec.
What is the best oil for a Hydro-Gear transaxle?
The factory's choice is 20W-50 engine oil, which is what Hydro-Gear's manuals recommend for normal operation. Hydro-Gear's own service kits contain its Commercial Transaxle Oil. Don't use biodegradable oil in a ZT-4400 or ZT-5400; Hydro-Gear hasn't approved it.
What does the Hydro-Gear 52114 filter fit?
Per Hydro-Gear's manuals: the ZT-2800, ZT-3100, ZT-3200, ZT-3400, ZT-3600, ZT-3800 and G700. The ZT-4400 uses 72537, the ZT-5400 uses 71943, and the EZT and T2 have internal filters.
What's in the Hydro-Gear 72750 kit?
5 quarts of Genuine Hydro-Gear Commercial Transaxle Oil, 2 Hydro-Gear Commercial filters, and a fitting and pump, for the ZT-2800 to ZT-3800 range.
How often should I change Hydro-Gear transaxle oil?
ZT-2800 through ZT-3800 and G700: first at 75–100 hours, then every 400 hours. ZT-4400 and ZT-5400: first at 100 hours, then every 400 hours or yearly, whichever comes first. The EZT and T2 are sealed and don't have a routine change.
How much oil does a ZT-2800 or ZT-3100 hold?
70.3 or 71.9 fl oz (2079 or 2126 ml) per transaxle, or 56.6 fl oz (1674 ml) with an internal expansion tank, not counting the external tank and hose. Plan on about 2 quarts per unit.
Does the Hydro-Gear EZT need oil changes?
No routine changes. Hydro-Gear's manual says it is factory filled, sealed and does not require oil maintenance; add or change oil only for contamination or degradation.
Sources: Hydro-Gear Oil page, FAQ, Cross Reference Guide; service manuals BLN-52622 (ZT-2100/2200), BLN-52441 (ZT-2800/3100/3200, Apr 2023), BLN-52441 (Jan 2023), BLN-0108 (ZT-3400/3600/3800), BLN-0081 (ZT-4400), BLN-0014 (ZT-5400), BLN-0094 (G700), BLN-52749 (T2), BLN-52503 (P Series pumps); Toro-hosted copy of BLN-51337 (BDP pumps). The 52114 cross-reference is from an aftermarket retailer's Stens TF738 listing, not Hydro-Gear.
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Related guides: ZT-2800 · ZT-3100 · ZT-3400 · ZT-4400 & ZT-5400 · Hydro-Gear pumps