i have a 1992 f250 idi 2 wheel drive.

I went out out of town for a week and the truck sat while I was gone, it’s had plenty of times where it’s sat for weeks and never had an issue. Went to drive my truck today and when I reveresed it out of the yard the brakes work fine. Then when I put it in drive, and I was barely doing 15 down the road and barely I tapped my brakes and I notice my rear left tire sounded funny so I pressed the brakes a little more and my rear left tire locks up and just slides. Any ideas?