First I took the approach any man would take, and since this was a manly job, I thought it best to start out in a manly fashion. I went out and tried to install the belt without any instruction. That didn't work. I knew where the belt had to go, but I couldn't figure out how the heck to get it there.
So, I decided to take the womanly approach (aka, common sense) and search for instructions. Like anyone else in this wonderful digital age (and like anyone who also has a Dad who loses manuals), I turned to google, to see how to thread the belt on.
Here are the instructions I found:
"John Deere 318 Onanhorizontal-shaft engine has a front-mounted PTO electric clutch that drives a pulley. A tension-adjusting spring-loaded double-pulley set is frame-mounted below the electric-clutch. This drive set has two pulleys attached parallel to each other but on opposite sides. Their axis is 90 degrees rotated compared to the PTO pulley. That drive set is attached to the frame by pins which fit into frame slots. Belt tension holds it in place. Insert your belt loop up through the drive set, wrapping it onto both drive pulleys.
If you wish, you may remove the drive set from the frame to start the belt fitting, but that's not necessary. Rotate the front drive set's spring-tension-adjusting knob until its indicator points to the position marked as "Install." Wrap the belt around the PTO clutch sheave which twists the belt a quarter turn between the PTO pulley and the two drive set pulleys. The belt runs down from the PTO clutch pulley, twisting 90 degrees onto the two drive set pulleys, then horizontally back, twisting in the opposite direction another 90 degrees then wraps around mower deck's drive pulley. To provide some slack during fitting, push the spring-loaded right-side drive set pulley "up" into the spring tension. After fitting the belt with V-side seated into each pulley wrap, rotate the mule drive's spring-tension adjusting knob until its tension-indicator points toward the drive set top. That applies the factory-suggested belt tension preload. If you encounter belt slippage during wet conditions as may occur when cutting juicy weeds which reduces belt-to-pulley friction, consider increasing belt pre-load tension as a compensation strategy. The factory spring-pre-load tension balances slippage against belt service life for the most commonly encountered conditions. When conditions are dryer again, reduce belt tension back to factory suggested value. Hope this helps."
Huh? By the way, I love that last line: Hope this helps. Those are the only three words I understand.
I admit, at this point, I was about ready to call Dad and see when he'd be able to come over and install this belt. I'm a girl, afterall. This job involves dirt, grime and sailor vocabulary.
However, my lack of patience overruled my sense of gender-driven biases, so I went back out to try again, after reading the techno-jargon half a dozen times.
After a little fiddling I finally was able to get the belt installed, but in order to facilitate anyone else researching the web and trying to figure out how to install a mower deck drive belt on a JD318, here's the translated installation instructions:
"Pull the two springy-things that attach the pully box dealy-bobber to the deck and it will release the box. Please ensure no small animals or your appendages are under the box as it will drop violently onto the ground with a thud, contaminating the pullies with dirt that will take you an extra ten minutes to clean before installing the belt. Now that the black box pully thing is on the ground, you can figure out how to wind the belt around the wheel in front, then down through those pullies and on through to the mower deck. Now try your best to re-attach the black box pully thingy whilst keeping the belt in position. Try again. Then try again. Then cuss. Then try again. Then cry. Then try again. Then celebrate with a little dance once you've gotten it attached. Then pull the belt back to its final pully-deal on the mower deck. Then realize that the belt came undone on the front part. Cry. Then try to re-thread it on without lowering the black box thingy again. Crush your finger. Cuss. Then realize you have to grow a third arm to complete this task. Then go inside and drink heavily."
Hope this helps,