Sierra 18-2591 Borg-Warner Overhaul Kit

Revitalizing your boat's drivetrain starts with reliable components, and the Sierra 18-2591 stands out as a go-to solution for Borg-Warner Velvet Drive owners. Designed specifically for the 71 and 72 series transmissions, this overhaul kit tackles wear from saltwater exposure, high torque loads, and years of marine duty. Boat enthusiasts know that these transmissions deliver that signature smooth hydraulic shifting, but seals dry out, gaskets harden, and internal components fatigue over time—leading to slips, leaks, or outright failure. With this kit, you're equipping your vessel with high-quality replacements that restore factory-level performance without the premium cost of originals.

Common Transmission Troubles and How This Kit Fixes Them

Picture this: you're out on the water, throttle open, and suddenly the shifts feel sluggish or you spot oil seeping from the bellhousing. These are classic signs of a Velvet Drive needing attention. The 71 series, often paired with engines up to 250 HP, and the 72 series for heavier setups, share vulnerabilities like degraded input shaft seals and worn output seals. Leaking fluid not only starves the clutches but invites corrosion in the marine environment.

This kit addresses those pain points head-on. It supplies all the gaskets, seals, and o-rings needed to reseal the unit completely. Think of it as a full refresh: new lip seals prevent fluid loss, fiber gaskets ensure airtight housings, and o-rings restore hydraulic integrity. Mechanics report that post-overhaul, these transmissions shift crisper and run quieter, extending service intervals significantly.

Kit Contents Tailored for Real-World Rebuilds

No guesswork here—every piece in the Sierra 18-2591 is precision-engineered for Borg-Warner specs. You'll find:

• Complete set of gaskets for case, cover, and adapter plates
• Input and output shaft seals to stop drips at the source
• Assorted o-rings for pumps, valves, and governors
• Converter housing gasket for seamless mating
• Filter screen and related hardware for thorough cleaning

Unlike partial kits, this one covers the essentials for a drop-in rebuild. Pro tip: inspect clutch packs and bearings while everything's apart; they're not included but often need attention in high-hour units.

Seamless Compatibility with 71 and 72 Series

Whether your boat rocks a 71C (straight in-line) or 72C (with reduction gear), this kit fits like it was cast for it. These transmissions powered everything from Chris-Craft runabouts to larger cabin cruisers in the '60s through '90s. Cross-reference with OEM part 71-01075 or 72-01075, but Sierra's aftermarket prowess means broader availability and material upgrades—like silicone compounds in seals for better UV and heat resistance.

Double-check your model: ratio tags on the case confirm 71 vs. 72. This ensures no mix-ups, especially on repowers where engine-transmission pairings vary.

DIY Installation: Tools and Tips for Success

Overhauling a Velvet Drive isn't weekend warrior territory for everyone, but with the right approach, it's manageable in a home garage. Gather a transmission jack, seal drivers, torque wrench, and ATF fluid. Drain and disassemble methodically—start with the oil pan, then tailhousing.

1. Clean all mating surfaces meticulously; residue causes 90% of leaks.
2. Replace seals with light lubrication; avoid petroleum-based lubes that swell rubber.
3. Torque bolts to spec (typically 15-20 ft-lbs); uneven tightening warps gaskets.
4. Prime the pump before startup to prevent dry run damage.
5. Break-in: Idle in neutral, then light forward/reverse cycles with frequent fluid checks.

Expect 4-8 hours for experienced hands. If clutches are glazed or thin, source those separately for a full rebuild. Post-install, monitor for unusual noises—early detection saves big.

Long-Term Maintenance to Maximize Lifespan

A fresh overhaul is only as good as your upkeep. Change ATF every 100 hours or annually, using Dexron III or equivalent. Check dipstick cold, engine off. Watch for metal shavings in the pan—a red flag for bearing wear. In saltwater boats, flush with fresh water post-use to rinse salt buildup. Many owners add a remote filter for easier servicing. With diligent care, these transmissions routinely hit 2,000+ hours before major work.

Sierra's reputation shines here: parts molded from marine-grade materials resist the brutal combo of heat, pressure, and moisture better than generics.