Postby Workshop Help » 02 Mar 2009 19:25
Well, actually, with the four speed it doesn't matter. It doesn't matter because the 4-speed derives all it's lubrication from the splash method, it has no pump. As such, good old staight 90wt or most any blend will do just fine unlike the oil pumper LT77 which is of a very different design evolution. Back in the 4-speed days for about 30 years, we would ocasionally drain and refill with 90wt, or 80-90wt, or 90-140wt, and it would shift and growl just the same. Once we tried adding a whollop of STP oil treatment like the U.S. Factory Racing team did on their Spitfires. No difference.
If you're still running a 4-speed, it will far outlast the average LT77. It doesn't need the constant oil changes to wash out the swarf in the sump to try and prevent the oil pump gears from being chewed up by the steel swarf being sucked into the intake pipe there in the sump. Whew! That is one long sentence. The bad side is the 4-speed as the wrong ratios in 1st and 2nd with direct drive 4th leaving the engine over rev at highway speeds, i.e. 3275RPM at 60mph versus our 2600RPM at 60mph with the 3.63:1 rear end ratio from the 4-speed car.
