This is a step by step process on how to install your underdrive pulley and/or replace your crankshaft pulley. Feel free to ask questions or comment.
If you want to purchase one, see here: http://www.aveoforum.com/forum/f104/...-2008-a-11233/
We start by jacking up the front passenger corner of the car and remove the wheel. Make sure to use a jack stand.
Next, we remove the splash guard around the corner of the engine bay. Remove the two nuts shown here (10mm heads)...
...and the bolt and nut (10mm heads) shown here.
Now, we're looking straight at the crankshaft pulley. This is the one semi-tricky thing to do. Thankfully the torque specs aren't real horrible on the Aveo. You have to remove the crankshaft bolt. It has a 17mm head. The easiest way to do this is with an impact wrench. If you do not have an impact (they're quite cheap for an electric one at harbor freight and its very useful), you'll have to get some help. Have someone shift into gear (or leave in park), and push the brake pedal down while you use a breaker bar (and possibly an extension) to get the bolt loose.
After the bolt is off, remove the pulley and accessory belt. It should separate from the timing belt pulley shown above. Take some care not to remove the timing belt pulley as this will cause a lot more work to be done.
Now, put the underdrive pulley on to the timing belt pulley. It should slip on a little snug and stay in place. If it doesn't, you'll have to hold it on while you tighten up the bolt to hold it on. I believe the torque spec is ~76 ft/lbs. There is a small key and keyway that must line up, so make sure that happens.
Next, install the accessory belt. I recommend getting a new belt sized 730k6 vs the stock 740k6 as I had problems with the stock belt squealing. To get the belt on, use a wrench on the tensioner to pry the belt tensioner. Do not do as I did with a crow bar. It works, but the wrench is better and easier.
Thats just about it! Your pulley is now installed. You just have to replace the splash guard, put your wheel back on, and drop your car back down. The whole process took me less than 30 minutes. The impact wrench is the key to making this easy.