Velvet Drive 71C Series

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

Short answer: The Velvet Drive 71C is the cast-iron 71 series in 1017 part numbers, from 1:1 direct drive to 2.91:1 reduction. Chris rates the 1.91:1 the best reduction Velvet Drive made; the 2.10:1 generates a lot of heat.

The 71C is the cast-iron 71 series Velvet Drive, in part numbers starting 1017. It comes as a 1:1 direct drive (like the 1017-004) and in reduction ratios, like the 1.5:1 (1017-005 and 006), the 1.91:1 (1017-008), the 2.10:1, the 2.57:1 and the 2.91:1.

What to know about the 71C

Chris thinks the 1.91:1 is the best reduction model Velvet Drive produced. Its planetary is fixed in place with a bearing and snap-ringed in two places, so it doesn't float. The 2.10:1 is another story. Its planetary floats on washers, and Chris calls it the worst transmission Velvet Drive did in the 71 and 72 series in-line configuration, because it generates a lot of heat. You can spot one because the return cooling line sits on top of the reduction planetary. On most transmissions the return port is elsewhere, but on the 2.10:1 they put a plug there and moved the return on top of the planetary.

Some late-1970s and early-1980s units used a collapsible spacer in the reduction housing, set at the factory with pre-torqued assembly tools. Don't reuse it. If you lay into it again with an impact gun, it'll crush and you'll have a sloppy back end. Put in a solid spacer, which is the current production part.

Velvet Drive switched from bushings to sealing rings in the case and planetary in September 1978. If yours still has bushings, that matters for neutral: a bushing-style unit will never hold a solid, positive neutral the way a sealing-ring one does, no matter how good the rebuild. The fix is a sealing-ring case and planetary, not another attempt at the one you've got.

Inside the clutch pack, the 71 series (1017) uses two snap rings, versus three on the 72 series (1018). There's a groove on top of the clutch pack pressure plate that looks like it's for a snap ring. The groove is for nothing.

Specs and duty ratings

Clutch clearance on a 71C, bronze or paper, is 0.018 to 0.053 in. The forward pack runs 4 steel plates and 5 friction, held with a snap ring in one of two thicknesses depending on the clearance you need, a thinner yellow one or a thicker pink one. The reverse pressure plate rides on eleven springs, part number 71-97, the same count as the 72C. Later units use eleven, not twelve. On one 71C Chris opened, the last rebuilder had added his own oversized spring to the set, and that one went straight in the trash.

What we look for on a teardown

A loose output coupling nut lets the coupling move in and out and beat against the bearing, cutting a groove in it. It's best to buy a new nut, because the nylon locking ring isn't really meant to be reused. Don't put copper washers under the pump bolts either. When we find them, we know somebody's been in there before.

Water shows up as a "strawberry milkshake" color inside. An overheated unit will have a phenolic washer that's gone brittle enough to snap. And clutch plate teeth should be perfectly square. When they start to chatter, that's significant wear.

Older bushing-style direct drives came with one reverse clutch plate, which was fine behind a small block like a 302 or 305. Current direct drives use two, which lines up with the bigger 350s and 351s people run today.

Watch the dowel pins if you're working on a 71. The 72 and 73 series use a bigger one, and if it ends up in a 71 it can indent the forward and reverse adapter housing and start a leak. Use the right size, and don't let a pin stick up above the top of the case.

We've also come across a part number that isn't in Velvet Drive's own model list: the 1017-202, with skinnier pump gears and a reverse pack of one bronze plate and two steel, instead of the standard two bronze and one steel. Chris's read is that it's a cheaper direct drive Velvet Drive built at some point, not a documented factory model. If you've got one, call us before ordering parts off a standard 1017 list.