The LP-600 series used two cylinders to both raise the tailgate and operate the packing panel. This design change was claimed to save maintenance by eliminating the two separate cylinders formerly used to raise the tailgate. All LP-600s can be spotted by their flat-backed packing panel (the LP-500 and LP700 panels are ribbed). Also note the triangular reinforcing brace pattern on the hopper sidewalls which was unique to the earliest 600s. Later models (and all LP-700s) reverted to the radial pattern of the LP-500.
The packing panel cylinders were relocated forward of the panel, inside the storage body (red highlights). Increased efficiency was claimed, but obviously the cylinders were now exposed to the compacted refuse load and much more susceptible to damage (a charge Gar Wood would level at a competitor's model after abandoning this method!)
The packer still operated basically the same as the LP-500, but raising the tailgate had a different procedure. As described in the patent, the rotary sweep panel (green highlight) as shown at position (A) blocks rearward movement of packing panel. Spring-loaded, one-way latch buttons (yellow) on either side of tailgate hold sweep panel elevation at hook (B). The operator then manually locked clevis pins into bores on either side of sweep panel (C) which locked it in position.
Conventional type tailgate clamps (not shown) were then released, and the packing cylinders energized. With the sweep panel locked and tailgate clamps released, the tailgate assembly was raised upward, ready to unload.
At this time, it cannot be verified if this method of "blocking" the packer panel to raise the end gate actually went into production, or whether another method was used.
The change in design to "multi-task" cylinders was likely in response to the Heil Colectomatic which used only two cylinders to perform both packing and tailgate hoisting operations. Ironically, a year after Gar Wood released LP-600, Heil did an about-face with their new Mark II, changing to separate tailgate cylinders and adding two more cylinders to the hopper bucket! To make matters worse, 1960 Heil had telescopic ejection compared to the conventional hoist-dump method used by other rear loaders. At any rate, Gar Wood seems to have had no problem selling the LP-600 or its successors.
Above: 1961 LP-600 in action (courtesy of Michel Ferro)