Yukon Gear & Axle Red Line MT-90 75W-90 GL-4 Manual Transmission Lubricant 1 qt — smooth shifting, synchronizer-safe

Red Line 50304 MT-90 75W-90 GL-4 is a high-performance manual transmission and transaxle lubricant formulated to protect gears and synchronizers while delivering smooth, precise shifting. Red Line MT-90 from Yukon Gear & Axle is a 75W-90 viscosity GL-4 manual transmission lubricant sold in a convenient 1-quart bottle. Designed for vehicles and applications that specify GL-1, GL-3, or GL-4 fluids, this oil is safe for brass and bronze synchronizers because it avoids the reactive sulfurs found in many GL-5 products. Its formulation balances wear protection and friction characteristics to reduce notchy shifts and extend component life.

How does MT-90 improve shifting performance?

The lubricant is engineered to deliver an optimal synchronizer coefficient of friction so gear changes are smoother both at temperature and when cold. That reduces gear clash and hesitation, especially noticeable during downshifts and quick lane changes.

• Balances friction for consistent synchronizer engagement
• Reduces notchy or sticky shifting even in low temperatures
• Helps preserve precise gear engagement under load

Will this fluid protect gears and synchronizers long-term?

MT-90 uses additives and base oils chosen for wear protection and thermal stability, helping gears and synchros resist scuffing and surface fatigue. Regular use helps extend component life compared with using improperly specified or reactive oils.

• Formulated for gear protection in GL-1, GL-3, GL-4 systems
• Non-reactive with brass and bronze synchronizers
• Promotes longevity through anti-wear and film-strength properties

Which vehicles and applications are compatible with this product?

This 75W-90 MT-90 is appropriate where manufacturers call for GL-4 or equivalent manual transmission and transaxle lubricants, and for systems that recommend special synchromesh fluids. It also matches requirements where SAE 75W-90, 80W, or comparable motor oil viscosities are specified for gearboxes.

• Manual transmissions and transaxles requiring GL-4 fluids
• Applications that must avoid GL-5 reactive sulfurs near brass synchros
• Vehicles calling for 75W-90 or similar gear oil viscosities

How do I use and store this 1-quart bottle safely?

Pour the fluid carefully into the transmission fill point when the vehicle is on level ground and the manufacturer’s recommended procedure is followed. Store unused fluid sealed and upright away from extreme heat or open flame; dispose of used oil responsibly per local regulations.

• Follow vehicle manufacturer fill volume and procedure
• Keep container tightly closed and store in a cool, dry place
• Recycle or dispose of used oil at approved facilities

Who is this for This product is aimed at DIY mechanics, professional technicians, and performance enthusiasts who need a reliable GL-4 manual transmission lubricant that is safe for brass synchronizers and built to improve shift quality. Choose Red Line MT-90 when you want an established, high-performance fluid in a handy 1-quart size for service work, topping off, or final oil changes where GL-4/MTL specifications are required.

FAQ

Q: Is Red Line MT-90 safe for brass synchronizers?

A: Yes. MT-90 is formulated without reactive sulfurs and is safe for brass and bronze synchronizers.

Q: Can I use this in place of GL-5 gear oil?

A: No. Use MT-90 where GL-4 or synchromesh fluids are specified; GL-5 contains additives that differ and may harm synchros.