Keeping your Rockford™, Twin Disc®, NACD® or WPT Power® over-center clutch in good operating condition is easy if you know follow these guidelines. This Foley Tech Tip will show you how to check your clutch for adjustment, how to adjust it, and how to keep it lubricated.
When to Adjust Your Twin Disc, Rockford, NACD or WPT Power PTO
The key to maintaining your clutch is knowing when to adjust it and, as with many things, this depends on how much and what kind of use it gets. You should monitor the force necessary to engage your clutch and if that force drops by 10-15% from the recommended engagement force ranges, your clutch facings (aka: clutch discs) are wearing and your PTO needs adjustment. Sometimes that is hard to tell day-to-day so a good rule of thumb is to measure the engagement force weekly during active use.
Note that when you replace your PTO or the clutch pack within it, you should recheck the engagement force after a day or so of use as there is often some settling after the first adjustment that will cause the clutch discs to loosen and the second adjustment should set you into normalized adjustment intervals.
How to Monitor Engagement Force
Engagement force measures the force to engage the clutch in your PTO: Too light and friction discs will not be held firmly causing wear in the disc or often excessive heat that can damage the clutch pack itself. Too heavy and you risk putting too much pressure on PTO components potentially damaging them and, more noticeably, making it harder to engage or disengage. There are two common locations to measure this force: 1) where the engagement handle meets the operating shaft there is often a socket fitting to allow you to use a torque wrench; or 2) You can measure the amount of pull from the handle at a specified height (force measurements for the two methods will be different). The chart below shows you the acceptable torque ranges for the most common sized PTO Clutches regardless of whether your PTO was made by NACD, Rockford, Twin Disc or WPT Power.
| DISC DIAMETER (# DISCS) | TORQUE AT OPERATING SHAFT lbf-ft (N-m) | HAND FORCE AT LEVER lb (kg) | HAND FORCE MEASUREMENT HEIGHT (“A”) |
| 8″ – Single Disc | 71/94 (96/127) | 64/85 (29/39) | 13.3″ |
| 10″ – Single Disc | 88/117 (119/159) | 79/106 (36/48) | 13.3″ |
| 11″ – Single Disc | 107/141 (144/191) | 97/127 (44/58) | 13.3″ |
| 11″ – Two Disc | 134/177 (181/240) | 121/160 (55/73) | 13.3″ |
| 11″ – Three Disc | 171/227 (232/308) | 98/130 (44/59) | 21″ |
| 14″ – Single Disc | 218/289 (295/391) | 125/165 (57/75) | 21″ |
| 14″ – Two Disc | 218/289 (295/391) | 125/165 (57/75) | 21″ |
| 14″ – Three Disc | 218/289 (295/391) | 125/165 (57/75) | 21″ |
| 18″ – Two Disc | 514/676 (696-915) | 218/288 (99/131) | 28.2″ |
| 18″ – Three Disc | 514/676 (696-915) | 218/288 (99/131) | 28.2″ |
How to Adjust Your Clutch
Here are the steps to take: Disengage the clutch, remove the inspection plate on the bell housing, and rotate the clutch until you can see and access the adjusting ring. Depending on the manufacturer and clutch the adjusting ring will be held in place by a “lock” of varying styles (i.e. pin you pull up, spring that is lifted up or screw lock that holds adjusting ring outer notches in place). When unlocked you will be able to rotate the adjusting ring to increase or decrease the engagement force. Rotate the adjusting ring counterclockwise to lighten force; clockwise to increase the engagement force for the clutch. Then adjust to obtain the proper handle engagement force for your PTO. When done, reposition the locking mechanism to lock in the adjustment you just made.
Want to see a video of the process? For Twin Disc and WPT Power click here. For NACD or Rockford click here.
Lubricating Your Clutch
Use lithium base #2 grease prior to installation of your PTO. Grease the release bearings (if not sealed), the main bearings (rotate the shaft by hand until the grease comes out), and the cross shaft. Once a PTO is installed, follow this schedule below.
Lubrication Schedule
| Bronze Collar Release Bearings | Every 8-10 hours of operation |
| Main Bearings | Every 8-10 hours of operation |
| Operating Shaft / PTO Cross Shaft | Sooner of 100 hours of operation or 3 months |
| Linkage and Levers | Use SAE 30 synthetic every 500 hours |
Finally, don’t over-grease your PTO. It may sound counter-intuitive, but we see a number of clutch failures every year due to over greasing. Most often in these cases the excess grease was absorbed into the clutch discs causing surface irregularities on the disc that, along with the grease, interferes with a tight clamping of the clutch discs, so the disc or discs slides when they shouldn’t and with the amount of force the clutch pack manages, they can heat up relatively quickly to high temperatures that if not addressed soon enough will damage the clutch pack as well as the clutch discs.
Please call us with any questions about your over-center or spring-loaded PTO. Foley Engines stocks complete PTOs, clutch packs, friction discs, and other maintenance parts. If in doubt about your NACD, Twin Disc, Rockford or WPT Power PTO, give us a call. We take tech support seriously and want to share our knowledge!
Manufacturer’s names, symbols, and numbers are for reference purposes only and do not imply manufacturing origin.
