Be careful about swapping ratios behind the HydraMatic. It has a fluid coupling, not a torque converter, so it's not as forgiving about breakaway torque from a stop and a smooth transition of power between gears. It's entirely possible you could end up at the wrong torque point in the curve when shifting, with no way to adjust the throttle pressure to get the engine back into the RPM range where it belongs. Converters virtually double the torque from the engine just before the input shaft starts to turn as the vehicle pulls away from a stop. This allows manufacturers to use higher gear ratios without sacrificing low-speed performance. A fluid coupling acts like a manual clutch, with little or no slippage when locked up, but no torque multiplication on breakaway. Converters have a maximum RPM efficiency of 90%, with 10% slippage even at its best lockup point. That's the reason for having a lockup clutch inside the latest generation of converters with computer control of the lock-in point.
Jerry
Last edited by Hotrod Lincoln; 03/06/2011 4:09 PM.
