If this isn't the right place to post, I can move it.

I have a 2000 Ford Ranger 4 cylinder, 4 speed automatic. I don't know much about trucks, this is my first vehicle but I'm learning. I've put about 10,000 miles on it since I bought it.

Just got back from a 5500 mile road trip with no problems (that is part of the 10,000 miles I've driven it), then this morning the truck started vibrating very loudly when going 35 mph or higher. I was worried it was something self-destructing in the transmission but I think its just the right speed for the seal and bushing to bounce around loudly on the driveshaft. I'm going to being taking the driveshaft off tomorrow along with the tail housing and replacing the seal and bushing, but I'm wondering what would have caused this to happen in the first place. Really hoping my transmission itself isn't damaged at all, the truck is shifting fine.

Thanks for any help, I'm new to the forums and hope to see you guys around.