Output nut backing off and output coupling damage

By Chris, Hale Marine · 40+ years rebuilding Velvet Drive and ZF transmissions
Short answer: A backed-off output coupling nut lets the coupling move in and out and cut a groove in the bearing. 4775L is the nut for a 1:1 direct drive; 1000-149-034 is the coupling nut for current reduction units and 1004/1005 V-drives. Either way, buy a new one; the nylon locking ring isn't really meant to be reused.

What Chris sees on the bench

  • A groove worn into the bearing where a loose coupling has been beating against it.
  • Wear on the output coupling itself. On a coupling off a 1013, the nut had backed off at some point and the coupling went up and down and wore a groove.
  • A worn chamfer edge on the bottom side of the output flange. That's where you look to see if the coupling ever loosened up.
  • A nut that someone had Marine-Texed onto the shaft because it had loosened up.

What causes it

The output coupling nut has a nylon locking ring, and that ring isn't really meant to be reused. When the nut loosens up, the coupling can move in and out and beat against the bearing behind it.

Which nut goes where

Velvet Drive uses two different output/coupling nuts, with different torque specs:

Full torque numbers by fastener are on our torque specs page, the one Chris films in the video below.

Fix and prevention

When Chris sets the nut, he fills the cavity behind it with Ultra Black Permatex, then uses the nut with the washer on it to seal the surface. Back in the 60s, 70s and 80s nobody used any sealant there and never had any problems, until one leaked. Some manufacturers, even ZF, use an O-ring in there to seal off the splines.

When to call

If you've got play in the output coupling or a groove on the coupling, call (804) 333-3677, Monday through Friday 9 to 3 Eastern, or email sales@halemarine.com.

Related reading: why you never paint the coupling face and our Velvet Drive torque specs.

Sources

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