Center Plate Snubbers Bring Quiet to a Twin-Disc Clutch
Center plate snubbers bring quiet to a twin-disc clutch
EVEN BEFORE the customer shut off the engine and walked into Mobile Diesel Service’s office, the technicians in the Southern Oregon shop knew what the issue was with his ’13 Ram 3500. The noise and distinctive rattle when the clutch was disengaged could be heard above the sound of air guns and shop compressors. The truck’s twin-disc clutch was in dire need of some TLC. By the sound of it, the most likely cause of the cacophony could be attributed to the antirattle snubbers being shot and no longer doing their job.
A year and a half earlier, the same rig had a slipping stock clutch. Mobile Diesel upgraded the 6.7L Cummins–powered pickup with a South Bend Clutch G56OK-HD twin-disc to handle the additional power gained from an exhaust, ECM tuning, and other modifications, which most likely contributed to the stock clutch’s early demise.
According to the owner, the rattling noise began several months earlier and had gotten progressively louder. Ruben Villalobos, an MDS technician who specializes in such matters, put the Ram on the rack and pulled the clutch. Sure enough, he could clearly see the hard plastic anti-rattle snubbers were
missing from the center plate of the clutch. Hence, the primary cause of the obnoxious rattling when the clutch pedal is depressed.
All twin-disc clutches make noise as a direct result of the center, or “floater” plate, which is the intermediate flywheel between the clutch discs, vibrating against the locating notches in the flywheel when the clutch pedal is depressed. There are numerous methods used by clutch manufacturers to damp the noise generated by the inherent movement of the floater plate. South Bend uses hard, button-like neoprene snubbers, one on each side of the four locating ears.
Why these snubbers fail is difficult to pinpoint. “A clutch is a wearable product, so it really comes down to how the truck is being used and how it’s driven,” says Manseil Washburn, the head of the South Bend Clutch diesel division. “Snubber failure in this instance could be attributed to the truck being hooked up to a trailer all the time. But it’s more likely hard jolts to the drivetrain, such as when spinning tires suddenly get traction, that flatten out the snubbers prematurely.”
Manseil says the loss of the tiny internal noise dampers can also be caused by one or more of them not properly fitting in the holes in the ears of the center plate, causing them to loosen prematurely. They may have also gotten hot from slippage, which can happen when backing up a trailer. Excessive heat leads to the plastic snubbers falling out or disintegrating. Or it could be a combination of all of the above.
One thing that is almost certain when one fails is the others will soon follow. The missing piece causes the center plate’s vibration to increase, which places even more force on the remaining snubbers. The good news is they are easy to replace once the clutch is out. South Bend typically sends a packet of the “Neoprene Anti-Rattle Center Plate Snubbers” (PN MV11-1) to customers free of charge.
“We haven’t made a change to those [snubbers] in a couple of years, but the newest versions have a little taper on the protrusion that fits into that center plate, so they’re going to be stronger
initially because they fit the hole better,” Manseil says.
As you see in the photos, Ruben replaces the snubbers and throw-out bearing (PN N070SA-HD), which also shows signs of wear. The rest of the clutch assembly still looks new—even after 70,000-plus miles. In the end, six hours of rack time and $60 worth of parts is all it takes to make a Ram’s obnoxiously loud clutch whisper quiet.
2. Mobile Diesel Service technician Ruben Villalobos uses a hydraulic transmission jack to do a lot of the heavy lifting when working alone, including removing the ’13 Ram 3500’s transfer case crossmember and the two-piece rear driveshaft.
1. Remove the plastic trim and six 5/16-inch bolts that secure the shifter to the G56 six-speed manual transmission, so the gearbox can be taken out easily. Note: Shift the transmission to Neutral to ease reinstallation.
PRO TIP:Before pulling the transmission, the electronic transfer case is shifted into four-wheel drive. This allows the front output yoke on the transfer case to be turned by hand, making it much easier to align the transmission input shaft with the clutch during reinstallation.
5. Before lowering the transmission/transfer case/clutch assembly, Ruben unhooks the frame clips that hold the DEF wiring harness so he can slide it up and over the transfer case without actually having to disconnect all the wiring.
6. Pro tip:Rent or borrow a 33-inch-long, ½-inch drive extension for your air-impact gun. The long extension really makes getting to the upper bolts that hold the bellhousing to the block a lot easier.
4. With the G56 six-speed manual transmission/transfer case assembly bolted to the jack, Ruben pulls out the four 15/16-inch bolts that hold the crossmember to the frame. Make sure you have a stout jack, because there’s about 450 pounds suspended above your head.
3. The hydraulic clutch slave cylinder is removed.
10. Here’s the cause of most of the clutch racket: missing anti-rattle snubbers on the twin- disc’s center plate, or “floater plate.”
11. Once the South Bend twin-disc clutch is taken apart, the old snubbers fall out. All are in different stages of damage and deterioration. Ruben installs new snubbers from South Bend (PN MV11-1), along with athrow-out bearing.
9. Before removing the clutch assembly, Ruben shows us where the manufacturer marks the position (red paint) of the components after everything is balanced. It’s critical the clutch goes back together with the parts in the same location.
8. With the transmission down, inspecting the throwout bearing is easy. This one is bad, so it is being replaced. Riding the clutch or sitting with the clutch pedal depressed for long periods of time will shorten any throwout bearing’s life.
7. The transmission is then lowered and moved out of the way.