Big Twin Transmission Oil 85W-140 – Conventional Mineral Gear Oil

Heavy-Duty Protection for Harley-Davidson Big Twin Transmissions

The Big Twin Transmission Oil 85W-140 is engineered specifically for Harley-Davidson Big Twin 4-, 5-, and 6-speed transmissions and final drives that demand extreme durability and smooth performance. Formulated with high-pressure additives and premium base stock, this oil reduces friction, minimizes wear, and delivers smooth, quiet shifting under heavy loads. Its distinctive red color makes leak detection easy while ensuring consistent protection for your transmission gears mile after mile.

Key Features

• Formulated for high-load Big Twin transmissions and gearboxes

• Compatible with 4-, 5-, and 6-speed Harley-Davidson Big Twin transmissions

• Extreme pressure additives protect against metal-to-metal contact and reduce gear wear

• Distinctive red color aids in quick leak detection and easy maintenance checks

• Provides smoother shifts, helping eliminate the common V-Twin “clunk”

• Quiets gear whine for improved riding comfort and transmission longevity

• Enhances wear protection to extend gear and bearing life

• Designed for 4-stroke applications using a conventional mineral base oil

Performance & Fitment

Perfect for Harley-Davidson Big Twin models such as Road Glide, Street Glide, Road King, and Softail with M8 or Twin Cam engines, this 85W-140 transmission oil offers unmatched protection and consistent shifting. It’s the go-to choice for riders who push performance and longevity, whether on long highway rides or daily use. Trusted by builders who demand precision, this oil performs exceptionally well when paired with Nowaskey Suspension and Hofmann Designs performance setups — keeping your drivetrain smooth, cool, and quiet.

Viscosity (Weight): 85W-140
Oil Base: Conventional (Mineral)
Application: 4-Stroke
Container Size: 1.05 US quart / 1 liter
Meets or Exceeds Requirements for: API GL-5
Dispenser Type: Bottle
Units: Each
Weight: 2.08 lbs
Dimensions (L x W x H): 8.26" x 4.68" x 2.55"