Red Line Primary Case Oil - 1 QT (12/Case Sold Ea) — Harley-Davidson Electra Glide Classic, Softail Heritage Classic, Softail Springer (1984-2006)

Red Line primary case oil is a synthetic fluid formulated for V-twin motorcycle primary chaincases with wet-diaphragm spring clutches. Engineered to balance friction for smooth clutch operation and reduced wear across Evolution, Twin Cam, and compatible aftermarket engines from 1984 to present.

Features

• Friction-balanced synthetic formulation
• Reduces clutch slip and improves power transfer
• Lowers operating temperature in the primary case
• Compatible with wet-diaphragm spring clutches
• Works in Evolution, Twin Cam, and similar V-twin designs

Specifications

• Brand: Red Line
• Manufacturer Part #: 42904
• UPC: 083522429047
• Volume: 1 quart
• Weight: 2.01 lbs
• Dimensions: 4 in W × 4 in L × 8.8 in H

Fitment

Fits 1984-present V-twin American motorcycles including Harley-Davidson Evolution, Twin Cam, and Indian Motorcycle models with wet-diaphragm spring primary clutches.

Frequently Asked Questions

Can I use this in a dry-clutch primary?

No — this oil is formulated for wet-diaphragm spring clutches only. Dry-clutch primaries require a different product.

Is this the same as Red Line MTL gear oil?

Yes — this primary case oil shares the same friction-balanced synthetic base formula as Red Line's famous MTL transmission fluid.

Will this reduce clutch slip on a modified engine?

Yes. The friction-balanced formula is designed to apply more power and reduce slip compared to standard synthetics, beneficial for modified and high-output engines.

How often should I change primary case oil?

Follow your motorcycle's service manual interval. Most V-twin riders change primary case oil annually or every 20,000 miles.