Snap rings installed wrong

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

Short answer: Snap rings have an up side and a down side and a specific spot in the clutch pack: two on a 71 series, three on a 72. Put one in the wrong place and it can apply too much pressure on the clutch pack.

Velvet Drive 71C 72C clutch packs 1017-004

Where they go

71 series: one snap ring on top of the forward clutch cylinder, holding it in place, and one on top of the top pressure plate, where the bevel (forward) return spring sits.
72 series: the same two, plus a third on the bottom of the clutch pack, underneath the bottom pressure plate. That one is the selective snap ring, and it gives you your clutch clearance.
The 71 and 72 series both have a groove on top of the pressure plate. The groove is for nothing. Repeat, nothing. Don't put a snap ring in it.

What Chris sees on the bench

A customer who complained of a faulty clutch pack had put the selective snap ring on top of the pressure plate, because he thought it needed to go in that groove.
Snap rings in the wrong place, with the larger, thinner of the two on top of the pressure plate applying too much pressure.
A reverse spring installed upside down. Its prongs are supposed to ride on the steel ring on the forward clutch piston.
An old steel spacer ring on the forward clutch cylinder. Velvet Drive found the metal ring cut grooves into the back of the forward and reverse adapter housing, and now uses a plastic spacer.
A snap ring with almost nothing holding it in place. Reuse one like that and eventually, under load, it'll pop off and the clutch pack will pull right off the input shaft.

AS171C Early Velvet Drive 1017-004 Transmission

Fix and prevention

Know your series before you start: two snap rings on a 71, three on a 72. Check the orientation of every ring. There's always a slightly higher tab, a slight point, that tells you which side is up. Don't reuse a worn snap ring. Chris figures the snap rings Velvet Drive gets nowadays must be coming from China. If you find the old metal spacer ring, update it to the plastic one. For a 72 series, we stock a snap ring kit ($450.00).

When to call

If you're not sure which snap ring goes where, call (804) 333-3677, Monday through Friday 9 to 3 Eastern, or email sales@halemarine.com. Chris talks to people all day long.