Noise in Gear: Damper Plate or Transmission?

1017-005 Velvet Drive Rebuilt Testing

The knock that goes away by 1,000 rpm

Chris tells owners the same thing. Asked about a low-rpm clatter, he told one owner to bring the rpm up to about 1,000: if it's the engine or the damper, the noise clears up. On another video he put it even more plainly: "It is not the transmission. The engine is running rough causing transmission clatter."

On our test stand we run a rebuilt 71C/72C at 535 rpm and can push it up to 864. Leave an engine idling anywhere around 600 to 700 rpm and you'll hear a knock or a bang when the transmission goes into gear. That's an idle-speed issue, not a sign the gearbox itself is bad. See clunks when shifting.

A worn damper vs. a failed damper

Worn is one thing: the transmission still drives fine, you just hear the clatter down low. A completely failed damper, sheared rivets or stripped splines, is a different animal. Asked what could cause no forward and no reverse at all with the engine running normally, Chris answered: "Damper is most likely the problem if you don't have Forward or Reverse." A dead damper isn't sending engine power to the input shaft in the first place, so neither gear does anything. Don't assume a "dead" transmission needs a rebuild before someone's checked the damper. See no forward but reverse works.

How to check it

• Idle the engine down as low as it'll comfortably run and listen for the knock, then bring it up past 1,000 rpm. If the noise disappears, you're looking at the engine or the damper, not the gearbox.
• Rule out a rough-running engine first.
• Checking the damper itself usually means pulling the transmission, so rule out idle speed and the engine before you go there.

Picking the right damper

Damper selection is the engine and boat builder's call, not Velvet Drive's. On the 5000 and Liberty series this matters at the parts counter: Velvet Drive changed the input shaft spline over a few generations, an early short spline built for spring-pack dampers, an intermediate version, and the current long spline that mimics ZF's spline for rubber-block (Centa or Vulcan style) dampers. Put the wrong damper on the wrong shaft and it can bottom out and damage the engine's thrust bearing. If you're not sure which shaft you have, check before you order a damper.

When to call

Not sure whether it's the engine, the damper or the transmission? Call (804) 333-3677, Monday through Friday 9 to 3 Eastern, or email sales@halemarine.com.

Related reading: clunks when shifting, no forward but reverse works and the full troubleshooting guide.