Never had this happen before. Last week a I started feeling a driveline vibration in my '86 C10, very slight at aroud 45mph on deceleration (acceleration you wouldn't feel it). I figured one of my ujoints was going bad, although I though that would be kinda of odd, being they were spicer joints, and only about 1 year and 20k mi old, and not subjected to anything harsh, totally stock 2wd driveline,suspension here. When I did that job, I also had the whole shaft balanced as well. It's a long bed and has three joints with the center bearing holdup. I drove the rest of the way home at 75mph about 70miles, drove around during the week aanother 100miles. Finally got under there today, and I find one of the middle joint caps half way out and the c-clip gone. The joint looked perfectly fine, but I popped in a new one anyway. How does an inside c-clip come loose after 20k mi and 1 year service. I've had them come loose before immediatly after installing, indicating I didn't properly install it, but after 1 year of service? Just gone. And how is it the cap didn't fly out going 75mph for over an hour. Is something wrong with my yoke or something? Just seems like a really odd problem.