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Proper lubrication with quality lubricants will ensure your GMN sprag clutch is operating at the highest efficiency and long life span.

When the sprags are in the freewheeling state, there is sliding contact between the sprags and the shaft and housing surfaces. So, there must be a film of oil to protect against metal-to-metal contact. If the oil film isn’t present or is not adequate, then excessive wear and premature failure would occur. However, too much lubrication can also cause the sprags to not engage properly or it can generate too much drag.

GMN Recommendations:
For oil bath systems, GMN recommends 1/3rd of the sprag clutch height is submerged.
For greased clutches, GMN recommends 30-60% of the available volume to be greased.

Some oils or greases, especially in engine or gear box applications, can have anti-friction (or EP) additives in the lubrication. While these additives are great for gears and other components, they hinder the performance of the sprags and can prevent them from engaging. These additives are designed to make sure a film of oil remains in place between the metal components no matter how much pressure is applied.

However, the sprags must be able to push through the oil layer and act directly against the metal shaft and housing when engaging or they will slip. For this reason, lubrication without these additives is required for GMN clutches.

Contact our in-house engineers to learn more about oil and grease additives that may be impacting your application's performance.

GMN Standard Clutch Lubrication

All GMN’s sealed clutches come lubricated for life with grease in the Ball Bearing units and oil in the Complete units. GMN can supply open clutches pre-greased, andstandard manufacturing lead times will apply.

The tables below show a few suggestions for both oil and grease lubrication that we’ve tested and proved to be successful. If you’d like another lubrication that’s not listed below, contact us so we can make sure it’s compatible and won’t result in failure.

Oil Lubrication for Sprag Clutches

  -15°C – 30°C
(5°F – 86°F)
15°C – 90°C
(59°F – 194°F)
60°C – 120°C
(140°F – 248°F)
Hydraulic Oil Hydraulic Oil HM 10 Hydraulic Oil HM 32 D Hydraulic Oil HM 100
Motor Oil   HD-Motor Oil SAE 10 WATF-DEXRON III HD-Motor Oil SAE 30

Motor oil lubricant is the type you find in the automotive section. Please note: HD-motor oil SAE 10 W or SAE 30 is equal to API-Service SE or CC or MIL-L-46152B.

Important: Only mix oils with the same type of material and components. For example, ATF oil should only be mixed with ATF oil and HD-motor oil should only be mixed with other HD-motor oil, etc. If there’s ever an oil brand change it’s necessary to clean the Sprag Clutch and all its mating parts. Never use trichloroethylene or perchloroethylene to clean any components.

Oil levels should be in relation to the size of the sprag clutch and one-third of the clutch (in normal position, not operating) should be submerged in oil.

Clean oil, free of moisture, should be sprayed directly onto clutches for oil mist lubrication systems. Daily inspection of open or unsealed housings will ensure proper lubrication levels.

For operating temperatures between 15°C to 90°C, our double-sealed sprag clutch series, FND and FPD, are filled with standard oil (unless you put a special request in with your order). Other lubrication types are available, contact us for more details.

Recommended Oil

-65 to 100º C-35 to 160º C15 to 90º C
Manufacturer Klüber
Isoflex PDP 38

Turmofluid SF 48
GH 6 oils

Turmopoloil HT
Tellus S2 MA 32
Oil Type Diester oil based Polygl.oil based Mineral oil
Characteristics Synthetic long-term oils Synthetic transmission
and high-temp oils
High performance
hydraulic oils

Grease Lubrication for Sprag Clutches

Some types of grease won’t work with our sprag clutch line, especially if they contain additives.

For example, lubrication additives like extra pressure (EP) additives for transmission or gearbox applications may prevent the sprag clutch from working properly. Greases from different manufacturers may not be compatible. Contact us with any questions or for proper lubrication recommendations.

Please note: There is no universal grease for all service and operating conditions. The table below lists tested and approved grease types for our sprag clutch products.

Klüber Lubrication ISOFLEX LDS18 Special A Lithium Ester/Mineral -30° C … 130° C
-22° F … 266° F
Deep temperature and long-term grease with high resistance to aging and corrosion.
Shell Alvania RS Lithium Mineral -10° C …120° C
14° F … 248° F
Long term grease with high resistance to aging and corrosion.
Klüber Lubrication Bio BM72-50 Polyurea Ester -20° C …120° C
-4° F … 248° F
Biological grease especially for overrunning and backstopping
Klüber Lubrication Synth HB72-102 Polyurea Ester -40° C …180° C
-40° F … 356° F
Synthetic grease especially for overrunning and backstopping

The correct amount of grease should cover approximately 60% of the free volume in and around the sprags of the clutch.

Recommended Greases

Operating Temperature-50 to 120º C-40 to 180º C-40 to 200º C-40 to 260º C
Manufacturer Klüber Isoflex
LDS 18 Special A

LUBCON Turmogrease
Highspeed L 252
Klüber Asonic
GHY / HQ 72-102

LUBCON Turmogrease
PU 703
BHP 72-102

LUBCON Turmogrease
NBI 300 P
Klüber Asonic
GHY / HQ 72-102

LUBCON Turmogrease
PU 703
Base Oil Mineral oil
Diester oil
Diester oil Perfluropolyether oil
Diester oil
Diester oil
Thickener Lithium soap Polyurea Polyurea, PTFE Polyurea
Characteristics Dynamically light long-term lub. grease Synthetic long-term lub. grease High temperature long-term lub. grease High temperature long-term lub. grease

Best Practices for Applying Grease

We recommend letting our technicians grease the clutch for you but if this goes against your standard operating procedure we understand. In that case, here are our suggestions for applying grease yourself:

  • Utilize a clean room
  • Use gloves
  • Use lint-free wipes
  • Change the air filter often in the room you are using

When we grease sprag clutches, we commonly use ball and roller bearing grease because it’s continually monitored for maximum quality and maximum clutch life. Sealed ball bearing clutches “RS” and “2RS” are shipped grease lubricated with standard grease Isoflex LDS 18 Special A.

Please note: If you decide to purchase your own grease or oil lubricant, we can’t endorse or guarantee the quality of our sprag clutch line. We recommend allowing our technicians to lubricate the GMN sprag clutch. For more information, contact us today.

Interested in GMN Sprag Clutches?

Check out our Sprag Clutch Guide resources below for more information.

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