Grinding noise from rear end?

[ActuallyaMazda]

Hello all! Hopefully someone here can help steer me in the right direction with this problem.

I have a '94 Mazda B3000 2WD and for a while now, it has been making a slight grinding noise at very low speeds that has gotten worse over time and is now quite noticeable. It doesn't occur while tracking straight at all, but if I am accelerating from a stop or at low speeds (No more than 10mph), it will start vibrating and shaking the pickup and almost feeling like it is binding. If I am making the same low speed turns and coasting, it will make a groaning noise that speeds up or slows down depending on how fast I am going. Sometimes, if I am accelerating too fast from a stop, it will feel like it slips and I lose all power until I release the gas pedal and press it again. I was originally chasing this as a Transmission problem, but I took my truck to work and put it up on a lift and the rear axle shafts felt like they had a lot of slop in them. I did my differential fluid about 3 weeks ago and the fluid didn't look the best, but there was also no metal in the fluid. Put new fluid in with friction additive and the problem seems to be getting worse since then. This morning it started sounding like it was making a howling noise at 60mph on the freeway.

If anyone else has had an issue with this, I'd love some input. I know the Torque Converters in these to be a common point of failure which is why I was originally chasing this as a transmission issue, but with the way the axles felt super loose (sitting on the ground, If I kick the tire it even sounds like things are loose and hitting against each other) and the howling on the freeway this morning, I am stumped. Any help is greatly appreciated before I bite the bullet and take it to the Ford dealer.

 

[Curious Hound]

What were you doing when you felt the slop in the axle shafts? What kind of mivement did you observe? Were the wheels on or off? About 1/8" movement in and out in each axle shaft is normal. If you were able to move the wheel flange up and down or side to side, that would indicate wheel bearu g failure.

Did you check for movement in the pinion shaft? (In/out, up/down, side to side) with transmission in neutral, how far can you rotate the pinion before a wheel starts turning?

 

[superj]

If you do S turns while driving down a straight road does it get louder when the truck is leaning one way versus the other. That will tell you if only one side is messed up because it will get louder when the weight is on it

 

[ActuallyaMazda]

What were you doing when you felt the slop in the axle shafts? What kind of mivement did you observe? Were the wheels on or off? About 1/8" movement in and out in each axle shaft is normal. If you were able to move the wheel flange up and down or side to side, that would indicate wheel bearu g failure.

Did you check for movement in the pinion shaft? (In/out, up/down, side to side) with transmission in neutral, how far can you rotate the pinion before a wheel starts turning?

Wheels were off when I felt the slop and it is while pulling in and out and it felt like it while it was rotating as well. It didn't feel like there was any play up and down or side to side. I did not check the pinion shaft. Late night in the garage and it totally slipped my mind to do. If that would be a point of failure for those symptoms, then I can absolutely pop the cover back off and check that.

If you do S turns while driving down a straight road does it get louder when the truck is leaning one way versus the other. That will tell you if only one side is messed up because it will get louder when the weight is on it

The issue presents itself turning either way. Once I get maybe 30 degrees of a turn past straight ahead to either direction it starts to make the grinding/groaning noise.