Impact damage vs. normal wear

By Chris, Hale Marine · 40+ years rebuilding Velvet Drive and ZF transmissions

Short answer: Normal wear leaves indentations where steel plates ride on the clutch gear teeth. Impact, over-revving or too much horsepower shows as bluing, welded clutch plates, graphite buildup, a cut piston or bearing spalling.

Customer request. Transmission Failure

What normal wear looks like

Steel clutch plates ride on the clutch gear teeth and leave indentations. That's normal.
Clutch plate teeth that are still square. When they start to chatter, that's significant wear.

What impact or abuse damage looks like

A customer asked us to show what happens when a transmission is over-torqued. The unit in the video is a 5000 Velvet Drive, but almost all transmissions have similar components. Here's what Chris pointed out:

The case and ring gear clutch assembly starting to turn blue, and clutch plates starting to show overheating.
Clutch pack plates welded together. Chris says that can happen if you hit something or you're over-revving.
Graphite material building up inside the clutch drum, and an overheated clutch hub with teeth marks and discoloration.
When you really overwork the transmission, the piston gets cut into, and pieces of broken clutch plate try to get out the relief holes.
Some spalling where the bearings ride on the shaft.

Chris says this is what happens to the internal components when a boat goes aground or you're putting too much horsepower through the transmission.

Other examples from the bench

A 1014-007 3:1 CR-2 with an overheated clutch drum and a reduction planetary whose teeth were getting shiny and starting to break apart. A good drum is nice and shiny with no problems inside.
A ZF63IV where the owner overheated the clutches. Chris wondered if it was an impact or a high-speed shift.
A 1017-006 with a chipped tooth on the reverse planetary, the bushings gone and significant wear on the thrust washer. Chris's read was that it had been run in reverse for forward.
A 1017-008 somebody had been into before: the forward piston hacked up, forward and reverse clutches burnt, and graphite and shavings from the clutch plates in the bottom of the case.

1014-007 3.0 CR-2 Velvet Drive Drop center Transmission

When to call

If your boat went aground, took a hard hit, or you're not sure what you're looking at inside a transmission, call (804) 333-3677, Monday through Friday 9 to 3 Eastern, or email sales@halemarine.com.