Anyone have problem with their posi chattering?

[o6r1man]

The posi unit in my 70 chatters bad when turning but only seems to do it when it gets some heat in it. All winter long I haven't had a signal problem, today I drove the truck about 40 hwy miles and when I got back to town and was going through parking lot I thought my rearend was going to lock up. It felt like the spiders were binding up and popping. Later after it cooled down I drove it about a mile and it was gone. But after a few miles it was back. It did it last summer also but as the cooler weather set in it went away. Today it got into the 70s and like clock work it came back. Anyone else have it porblem? I pulled the plug and it was full of fluid..