Be careful about overfilling any manual transmission. The fill plug is situated in the case to be just below the centerline of the input/output shafts, and if the box gets overfilled the excess will try to find its way out past the seals on both ends. Some slip yokes have a tiny vent hole centered up in the back end just ahead of the u-joint, and lube can find its way out there and make a very hard-to-locate leak if the vehicle is parked in a slightly nose-up attitude. Up front, grease can find its way into the bellhousing and do a number on the clutch when you park on a downhill slope. Keeping the lube level a bit below the plug doesn't hurt, as the grease gets circulated by the spinning gears. If I'm flat-towing for any distance with the driveshaft installed, I'll jack up one side and overfill the box slightly to be sure the slip yoke and the mainshaft bearings get good lubrication. I towed a Datsun 510 from California to Tennessee that way.
Jerry
