Posted by David Sherman on Thursday, April 19, 2007 at 21:43:00 :
In Reply to: Rockwell transfer case pto posted by Jerry in Idaho on Thursday, April 19, 2007 at 19:03:34 :
I have a truck with the t-case PTO, but it's still snowed in so I can't get you a picture. You're smart to remember the oil pump and oil line. If you leave them out, you'll eventually wreck the upper bearings on the main shaft.
The reason for pump is that in normal operation, the bearings on the main (upper) shaft depend for their lubrication on oil that's carried up on the gear train from the bottom of the case. When running the T-case in neutral, the lower gears don't turn, which means that the upper shaft doesn't get oiled. This is also why they advise keeping the T-case in gear and the tranny in neutral when flat-towing an M35 for a long distance.
Since the PTO is normally run with the T-case in neutral, they needed a way to oil the upper bearings. For a short time, such as raising or lowering a dump bed, it's probably not necessary to have the oil pump, but for other uses, it's important. The way it works is that the T-case PTO contains a jaw clutch that engages the back end of the upper shaft, and a cam which runs a simple piston pump. A metal tube connects the pump to a port at the lower back corner of the T-case. I can't remember if there's a plugged hole there on a standard T-case or you have to drill and tap one when you install the PTO. The pump works by suction, so when you assemble it for the first time, you should probably prime it or at least make sure the piston is oily so it has some suck to it.
One of the neat things about the T-case PTO is that you have a full range of speed/torque selections via the transmission.
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