The advantage to the 4X3 is the ability to split a gear up or down if necessary to keep the engine in its best torque range. Generally, the Brownie will have an underdrive, direct, and overdrive ratio. For running unloaded, or lightly loaded, just leave the Brownie in direct, and shift the 4-speed normally, If you start to lug down on a hill, the under gear lets you pick up a few RPM without downshifting the main box. Ditto for gaining a little speed if you start to run out of RPM in direct- - - -just put the Brownie in OD and keep on trucking! One precaution- - - -don't use compound low in the main box combined with OD in the Brownie, as it wears out the bearings and gears in the main trans unnecessarily. It's best to split gears in 2nd., 3rd., and 4th. gear only. On the 5-speed OD transmissions we used in the big rigs, we didn't use OD in the main box combined with UD in the Brownie for the same reason. With both boxes in OD and a long, flat road, the speeds we could get were outrageous! Of course, once the rig was in motion, we never used the clutch. Just float the RPM right, and both transmissions could be shifted without using the clutch. Just don't get them both in neutral at the same time!
Jerry
Last edited by Hotrod Lincoln; 11/27/2009 2:41 AM.
