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Velvet Drive Troubleshooting: Symptom to Cause

By Chris, Hale Marine · 40+ years rebuilding Velvet Drive and ZF transmissions
Short answer: Velvet Drive's own service manual sorts problems into five buckets: leaks, no drive either way, drive in only one direction, trouble in neutral, and noise or vibration. Start with fluid, the shift cable and the damper before assuming the clutch packs are bad.

Velvet Drive's own service manual splits every problem into five buckets: leaks, no drive in either direction, drive in only one direction, trouble in neutral, and a miscellaneous bucket for noise and vibration. Start with the cheap checks below before anyone pulls a transmission apart. Every section here links to the full page on that symptom.

Start with the cheap checks

  • Fluid level and color. Check it warm, in neutral, with the engine off, and read it right away; fluid drains back from the cooler once the engine's been off a while. See maintenance by model.
  • The shift cable. Disconnect it at the transmission and move the lever by hand. See checking the shift cable.
  • The damper plate. A knock at idle that clears up above about 1,000 rpm is usually the engine or the damper, not the transmission. See damper plate noise in gear.

None of these cost anything but time, and all three can look exactly like a transmission failure.

No drive either way

Velvet Drive's chart for a transmission that won't move in forward or reverse points to low or no pressure: a jammed regulator valve, an internal leak, a bad pump, the wrong-weight oil, a pump indexed for the wrong rotation, or a blocked inlet screen. On a 5000 or Liberty, add a clogged suction screen, a broken prop, prop cavitation or a blocked cooler line to that list. See low transmission pressure and no forward but reverse works.

There's one more cause that isn't really a transmission problem at all: a completely failed damper plate can take away drive in both directions while the engine still revs normally. See damper plate noise in gear.

Only forward or only reverse

Lost reverse on a 71 or 72 series is usually shattered reverse plates; see lost reverse. No forward with reverse still working often comes back to a pressure problem: in Chris's experience forward needs more pressure to hold than reverse, so a slow internal leak shows up in forward first. See no forward but reverse works.

Problems in neutral

The factory chart blames a unit that drives forward in neutral on broken sealing rings or bushings, warped forward plates or a blocked control-valve exhaust. On an old bushing-style case (built before about September 1978), a little creep in neutral comes with the design and a rebuild won't cure it. If the gauge reads the same in reverse, neutral and forward, we look at the selector valve. See creeping neutral and selector valve problems.

Leaks and fluid loss

Velvet Drive's factory chart splits leaks into a few types: a bad seal or rough shaft, a rough bore, a loose or bad gasket, and one that surprises people: fluid loss with no trace anywhere. The factory points that one at the cooler or cooler lines. Oil coming out of the breather is a different, visible symptom, caused by overheated fluid, the wrong level, or water in the oil. See finding and fixing transmission leaks, water in your transmission fluid, front seals blowing out and output nut backing off.

Noise and vibration

The factory's miscellaneous bucket covers a hydraulic buzz (usually low oil or trapped air, or a sticking regulator valve) and gear noise (broken or pitted teeth). Noise in both forward and reverse points at damper misalignment or output misalignment rather than the clutch packs. See damper plate noise in gear, clunks when shifting and snap rings installed wrong.

Overheating

Across every Velvet Drive family, fluid that's crossed 190 degrees Fahrenheit has to be changed, in the transmission and the cooler system both. Watch for fluid that's changed color or smells rancid. See overheating transmissions, impact damage vs. normal wear and metal on the dipstick.

When it's the damper, not the transmission

A knock or clatter that only shows up at idle or low rpm, and clears up once you're above about 1,000 rpm, is how Velvet Drive's own manual describes a damper problem, and Chris adds a rough-running engine to that list. It's not a transmission problem. Don't let anyone start a rebuild before that's been ruled out. See damper plate noise in gear and clunks when shifting.

Actual pressure numbers

Everything above is deliberately relative. For real psi numbers by family, rpm and spring color, see Velvet Drive pressure specs.

Still stuck?

Call (804) 333-3677, Monday through Friday 9 to 3 Eastern, or email sales@halemarine.com. Tell us what you've already checked and we'll get you to the right page faster.

Common questions

My Velvet Drive has no forward or reverse but the engine runs fine. What's wrong?

Check pressure, pump rotation, the shift cable and the damper before assuming the clutch packs are gone. A completely failed damper plate can take away drive in both directions with the engine running normally.

Why does reverse work but not forward?

In Chris's experience forward needs more pressure to hold than reverse, so a slow internal leak tends to show up as no forward first, even when the underlying problem isn't specific to forward at all.

Is a knock at idle a sign my transmission is failing?

Usually not. A knock or clatter that only shows up at idle or low rpm and clears up above about 1,000 rpm points at the engine or the damper plate, not the transmission.

What does metal on the dipstick mean?

A few small particles are normal wear. Large chips or a lot of particles can be an early sign of failure, and rubber particles point at cooler-line wear instead.

Sources

Public documents we used for this page. Links open other websites in a new tab.