Strange noise!!!

I have 2000 express G 1500 with 110000 miles on it. Gives about 15 miles/gal. Lately, I have experience some strange noise while driving down on a down sloping hill. Without applying the accelerator, the van runs ok, but I hear some kind of sound from the back part the vehicle. May be from wheels or axle???? I have no idea. Any sugestions.
Thanks.

My '92 G30 (350 TBI, 4L80E, 270k) just started to make a weird noise when it is cold, and when idling or driving slowly. I think it is related to the power steering pump, but is weirder than what I am used to hearing. It sounds almost like a train whistle, and is pretty loud, but only lasts for about 15-20 seconds then stops. It sometimes starts doing it again after a few moments, or when driving less than about 10 mph, after which I don't hear it again until I slow down. The vans spends most of its days parked in the driveway until some big chore is needed.

I have 2000 express G 1500 with 110000 miles on it. Gives about 15 miles/gal. Lately, I have experience some strange noise while driving down on a down sloping hill. Without applying the accelerator, the van runs ok, but I hear some kind of sound from the back part the vehicle. May be from wheels or axle???? I have no idea. Any sugestions.
Thanks.
I had a noise in my full size Chevy van when going down hill with my foot off the gas a cluck,cluck,cluck noise ...I finally located the problem it was a loose universal joint ! at the rear axle ! It was not a bad universal joint but it had loosened up and was slopping around in the mounting clamps ...I could slide it back and forth by hand in the clamp ...I fixed it by taking the MOUNT clamp apart and filing the mount clamp cap with a flat file a little bit to make it fit a little tighter on the universal joint ... That was it ! works fine now no noise ... Bob in Michigan

I had a noise in my full size Chevy van when going down hill with my foot off the gas a cluck,cluck,cluck noise ...I finally located the problem it was a loose universal joint ! at the rear axle ! It was not a bad universal joint but it had loosened up and was slopping around in the mounting clamps ...I could slide it back and forth by hand in the clamp ...I fixed it by taking the MOUNT clamp apart and filing the mount clamp cap with a flat file a little bit to make it fit a little tighter on the universal joint ... That was it ! works fine now no noise ... Bob in Michigan
Thnaks Bob,
Can you please pinpoint me where exactly that universal joint is located at?