What fluid for a 4-speed trans?
Take this comment for what it's worth, since I have an automatic in my Dodge... but my other hobby car is a an 85 Celica Supra with a manual transmission. The general consensus in 80's Supra circles is exactly what
@scatpackbee said: Red Line MT-90. I put the MT-90 in the Supra and it's not a little better, it's WAY better.
From the Red Line website at
MT-90 75W90 GL-4 Gear Oil
- 75W90 GL-4 gear oil (similar to SAE 5W40/10W40 engine oil viscosity)
- Popular in Nissan, Mazda, Mitsubishi, VW/Audi, Lotus Elise/Exige, Toyota, Mendeola transmissions and Atlas transfer cases for Off Road
- Offers quicker shifts, perfect synchronizer coefficient of friction
- Safe for brass synchros, as it lacks the reactive sulfurs found in most GL-5 oils that cause damage
- High performance gear protection and longer synchro life
- Eliminates notchy shifting, even when cold
- Satisfies the gear oil viscosity requirements of 75W90, 80W90, 90 and motor oil viscosities of SAE 40, 10W40 and 15W40
- Recommended for GL-1, GL-3 and GL-4 applications, as well as where most special synchromesh fluids are specified
