Dual-Clutch Transmission: Wet or Dry?

Original Article ↗ Hacker News Discussion ↗

Wet vs Dry Dual-Clutch Transmissions (DCTs)

  • Many commenters strongly prefer wet DCTs due to better heat management and durability.
  • Dry DCTs are criticized for heat issues, seal failures, and contamination of clutches by leaked lubricant; one high-profile class-action around a dry DCT is cited as reputationally damaging.
  • Counterpoint: dry clutches are more modular and self-contained, making clutch-only replacement easier and potentially cheaper long-term.
  • Wet systems require regular fluid changes; some manuals allegedly recommend overly long intervals, seen as marketing rather than engineering-driven.

Broader Transmission Landscape (ZF8, CVTs, DCTs)

  • Modern automatics (e.g., ZF 8-speed) are praised for fast shifts, high efficiency, and reliability, seen as “peak” traditional automatic tech.
  • Belt-type CVTs on internal-combustion cars are widely condemned as unreliable and unpleasant, though some later units are said to be improved.
  • Hybrid “eCVTs” (planetary + motors) are emphasized as fundamentally different from belt CVTs and generally well-regarded.

Manual vs Automatic: Efficiency & Driving Experience

  • Enthusiasts value manuals for control, simplicity, durability, and “machine empathy,” but acknowledge modern autos and DCTs often match or beat manuals in fuel economy via more gears and smarter shifting.
  • Some report beating EPA numbers in manuals through careful driving; others report exceeding ratings in DCTs with no special effort.
  • Manuals are seen as painful in heavy city traffic; some would still choose them for mountains, snow, and off-road situations.
  • A few DCTs and autos offer manual modes that mostly obey driver commands, but limits (e.g., auto upshift near redline) frustrate purists.

Hybrids and Power-Split / Generator-Based Systems

  • Toyota-style power-split devices (multiple motor-generators + planetary gearset) are admired for simplicity and efficiency, replacing starter, alternator, and conventional transmission.
  • Honda and Nissan generator-style hybrids (engine mainly as generator, motor drives wheels) are seen as elegant; Honda adds a lockup clutch at cruise.
  • Debate over whether simulating gear shifts and RPM changes in hybrids is desirable or just pandering to expectations.

EVs and Transmissions

  • Many note EVs largely eliminate multi-gear transmissions, though some argue a 2-speed (or dual-motor / dual-ratio) approach could improve highway efficiency.

Motorcycles & Wet Clutches

  • Wet clutches are standard on most motorcycles and considered robust, though they contaminate oil with friction material.
  • Some bikes and a few cars offer DCTs; motorcycling is suggested as an outlet for those lamenting the decline of manual cars.