I'm a little stumped by the noise.
 

All, it's been a long while. My '03 Disco II has been in good hands for the last two years and is finally getting more miles thanks to it being the most reliable thing I own at the moment- never thought I could say that, but here I am.

So about a year ago I started to notice a squealing noise when accelerating. Okay, I wasn't too concerned because I was busy with other things in life and wasn't putting many miles on the old girl. I've been DDing the Disco for the last three weeks and I've been trying to focus on determining what the noise can be. The brakes are relatively new, and the fluid is of proper spec and topped. I did replace the front driveshaft two years ago and it has been kept greased. Again, the squealing happens on acceleration (I'm 99% sure of that), never at idle or when parked, and it gets quieter past 30mph, silent by 40ish. It hasn't gotten any more noticeable as I've driven it. I do notice that when I hear it occurring, if I step on the brakes, it does go away instantly. BUT here's the kicker- the squeal isn't always there, some days the Disco doesn't do it at all. I've tried many times to apply the brakes and let of the wheel to see if it biases toward one side or another, and no, the truck maintains a straight conveyance.

Can this still be the brakes?

EDIT (Forgot to mention): On occasion the three amigos will light up, but they haven't since I last topped the brake fluid a few weeks ago. I don't know if that has anything to do with it.

While I'm at it, I figured I'd ask another question possibly unrelated: With the front driveshaft changed out, should I also consider replacing the rear driveshaft soon? Even if it's not the cause of any issues right now?

Thanks.