My truck got to knocking today ,well more like a steel playing card in a bicycle spoke sound. I have a 94 K1500 6.5td . Anyways I pulled into a parking lot a checked it out . It defently was coming for the front pass side of the engine so I decided to pull the belt to see if it was one of the Acc's . The knocking wasnt there anymore so it has to be one of the acc's and the AC was off (clutch was disinguaged I double checked) so that leaves the Vac pump and maybe the water pump as suspects .

Now Im going to back this story up to a week ago when I had another Knocking problem. I was in the mountains between Cherokee NC and Gatlinburg Tenn going on up when my truck got to making a simular knocking noise.The truck was loaded down pretty good and had been for the 7 hour drive up there with the AC on the whole time. Well when it got to knocking I pulled off on one of those scenic over looks and checked it out. It sounded like it was coming from the same area as this knock . I cut the AC off and the knocking stop but the AC hasnt worked since.

Do yall think they could be related problems or 2 seprate problems . I know the Vac pump runs some of the AC controls on my truck.
TIA

Nobody ..
Another question is do yall think it would be ok to drive about 120 miles with the dead/ dieing pump . I have another ordered but it will not be in till tomorrow eve.

As far as the AC goes, is the compressor getting power?
If the Vac pump is noisy and you can wait for a replacement I would. have you checked the harmonic balancer as well?

My vacuum pump has been knocking since I got my 6.5 3 years ago and 21,000 miles ago. It still pulls 25" vacuum no problem, just noisy. I've noticed there the loudest at low speeds. Your A/C could have been slipping the belt which would have slowed the vacuum pump down.

Sounds like the compressor is done in, Just unplug the compressor, as the ac can and will cut in when the fan is on defrost, if you run it the compressor it could sieze and bust a fan belt, leaving you stranded.