Weird noise coming from driver side, Somewhere between differential and wheel Options

[Delta_Phoenix]

OK so the Celica has been making a weird noise for a couple months now. It started out with a popping noise whenever I got on it, or whenever I completely let off the gas while in gear. It's gotten worse since and now it pops constantly whenever I get on it, and I also hear a grinding/gurgling noise after driving for a long period of time. I've jacked the car up and let it run to see if it will still make these noises if there's no load on the front wheels. I went through all 5 gears, and never heard anything abnormal. The driver side axle wasn't making fluid movements though. The entire axle shaft was shifting up and down a little bit. I checked the other axle to see if it was a normal thing, and it was staying straight.

So far I've noticed that if I'm turning to the left and taking load off the driver side, the noise doesn't happen. It always happens when going straight, and sometimes is more pronounced if turning right.

I took it to my buddy, who is ASE certified and has quite a few years of experience, to get a diagnosis. He checked the tranny fluid, looked around for signs of rubbing/grinding, and eventually he came up with the idea that my differential is going out in the tranny. I'm not saying I don't trust him, but I've never heard a tranny make this sort of noise.

I've also checked the wheel bearings and ball joints, they're fine. Also checked the tranny mount, it's got some wear but nothing big.

Personally, I think something is wrong with my CV joints. The popping noise I hear sounds typical of a faulty CV joint, but the grinding and gurgling I hear is something new to me.

Any opinions or a possible diagnosis?