OK, so I'm a Rock Band fan, but I like to play it with a GHWT genericaster. Unfortunately, the strum bar on my GHWT guitar became very squeaky over time, and it was driving me nuts. First I tried this fix, which didn't help at all. Eventually, I went on a mission to fix it and was successful. Here is my method, step by step. My GHWT guitar is for the Xbox 360; if you have another system or another variant of this guitar there may be some minor differences in the guitar (different screws for example), but hopefully this general method will still work for you. Note that this method requires opening the guitar, which voids the warranty, but if your guitar is squeaky, the warranty is probably already expired anyway.
DISCLAIMER: I take no responsibility for any damage to your guitar that may result while attempting this process.
Things you need:
can of WD-40 lubricant spray
Torx T6 screwdriver
Torx T10 screwdriver
1. Remove the neck of the guitar using the locking lever on the rear of the body at the base of the neck.
2. Unlock the faceplate with the lever on the back of the body at the bottom of the guitar, and pop it off.
3. There are 11 Torx T10 screws in recessed holes on the front of the body. One of these screws is covered by a silver warranty sticker, which you must remove. Remove these 11 screws. Do NOT remove any screws that are not recessed, you may detach something inside the guitar.
4. There are 4 Torx T6 screws on the front at the base of the neck, remove these screws also.
5. You should now be able to easily separate the front and back of the guitar (if it doesn't come apart you probably missed a screw). Put the back of the guitar aside - all of the internal electronics are attached to the front.
6. Flip the front over and take a moment to survey the internal components. There are a few pieces that are likely to come loose - particularly the 3 pieces that allow you to attach the guitar strap. You might just want to put those aside as well. Also take a look at the whammy bar mount - the whammy bar may pop out while you are working on the guitar, but it's easy enough to slide back into the mounting grooves.
7. OK, now for the important stuff. In the center of the guitar is a small raised circuit board mounted above the back of the strum bar. If you peer under this, you will see two metal tabs that are resting on the back of the strum bar, one on each side. These tabs activate the switches that detect when you strum. I also found them to be the source of the squeaking in my guitar - as the plastic strum bar rubbed against those metal tabs, it was generating the very annoying squeak.
8. Spray the Q-tip with some WD-40. DO NOT SPRAY WD-40 INTO YOUR GUITAR. Take the Q-tip and gently rub some lubricant onto the end of each metal tab where it overhangs the strum bar, on the side where it contacts the strum bar (this will be "underneath" from your current perspective). You don't need to force the Q-tip between the tab and the strum bar - that might bend the tab and damage your guitar. Just get the end of the tab where it goes over the edge of the strum bar, strumming should do the rest.
9. Do some test strums to see if your squeaking has stopped. If so, congratulations, you just fixed your problem.
10. Before replacing the back of the guitar, check that the strap mount pieces and the whammy bar are all in place. Trust me that you don't want to put 15 screws back and then realize one of these pieces isn't in, I speak from experience.
11. Replace the back of the guitar, then flip it over and put all 15 screws back in.
12. Replace the faceplate, engage the faceplate locking lever and slide the neck back in. You are done!
I hope this procedure is helpful to someone.