Wheel Squeak While Driving

Ok, I've had this problem for a long time and I need to fix it. This is on my 95 GT.

While driving, there is a very loud squeak coming from what seems to be my rear driver's side wheel. The pads and rotor are fairly new, so it's not that. The squeak seems to be in sync with the wheel rotation, meaning when I go faster, it gets more frequent, etc. If it rains, the squeak is gone for a few minutes and then starts up...so somehow something is being lubricated and stops the squeak for a while. Also, it seems to get worse when I turn left, and slightly better when I turn right.

Any ideas on what this could be?

I've taken it to the mechanic and twice they failed to fix it.

Just because the brakes are new does not mean they aren't the culprit. If the calliper slide pins are sticking than it can cause the brakes to squeak, among other things.

It also very well might be the axle bearings. The only way to access these it to pull the axle out. You have to remove the brakes, open up the differential, remove the gears, and slide the axle out. It's usually a good idea to do both at the same time. And if you have a Trac-Loc, you might also want to consider rebuilding it at this time so you won't have to in the future.