Bad U-Joint???

I wanted to say thanks to everyone on the forums for all of the help that your advice is. I have saved much time and money from dealing with stealerships thanks to reading these posts. This is my first post so go easy. I have a 2000 z71 x-cab with 97K. Its got a 6" ProComp and 33" BFG AT's. It recently started making this grinding sound when the truck is in motion. it sounds almost like one of the brake pads is rubbing the rotor but there's nothing there. I've checked everything and come up with nothing. A friend suggested that maybe the U-joint is bad. I there any way I can tell if the u-joint needs changing? the sound is definitely coming from somewhere behind the cab. either from the rear wheel or under the bed. When I reverse, the sound goes from being a scraping/grinding sound to more of a high pitched whine.

Thanks

If it was a u-joint , the sound would change. When you speeded up the sound would get faster not louder and vice versa when slowing down. It is possible that you have a sticking cable for your emergency brakes and the shoes are rubbing on one side. That kinda sounds more like it the way you describe the sound changes when going in reverse. The Emergency brakes on your truck are located on the inside of the rear rotors. That is why the rotor is shaped like a hat , disc brakes on the outside and drum brakes for the emergency brakes on the inside.

Here's an easy way to rule out the U-joint. Have a friend put the truck in gear and then in reverse (while e-brake is on) you look under truck while freind does this a bunch of times. You will see the slop in the drive shaft u-joint everytime direction is changed.

Here's an easy way to rule out the U-joint. Have a friend put the truck in gear and then in reverse (while e-brake is on) you look under truck while freind does this a bunch of times. You will see the slop in the drive shaft u-joint everytime direction is changed.

Skipr is right.

Try this also:

Look at the u-joint. Is it seated probably in the yoke. it should look like a clean + pattern The reason my u-joints go bad is the needle bearings fallout and the + pattern looks more like a X with the inside of the u-joints is riding on the cap.


I hope this helps.
If you got big tires and you rag on your truck the OEM u-joints are bad.

Check out Tom Woods stuff. Very heavy duty. I have tried several times to break his stuff and today still can not.

http://www.4xshaft.com/


I broke my transfer case before I broke it drive shafts and u-joints.

i had the same conditions and it was the front ujoint of the rear drive shaft, but i did change them both..mine started this whining at 80,000 and when i put the truck in reverse it sounded just like the tire was squeaking or like the brakes were rubbing..but is was a the ujoint.....oh yeah my truck..99 silverado 5.3 ext cab 4x4....hope this helps....

Get under your truck and pull the drive shaft up and down, if you can hear it click with this, change the u joints with greasable ones, I als ohad asimilar grinding noise from the rear that was driving me crazy, turned uot to be the little turn wheel thats used to adjust the parking brake pads broke off, and got stuck between the disk. As soon as th disk came off in the inspection, the piece of metal dropped to the floor, the noise disappeared forever.

Yeah, It was the U-joints. It was the front u-joint on the rear driveshaft. I changed both just in case. The front U-joint's needle bearings were totally gone. The rear was starting to get worn down real bad. The sound is gone though. I did tak out the shoes in the rear for my parking brake and I was wondering what i should do for new ones. I remember reading in a post a while back that GM had a newly designed clip for the parking brake shoes to prevent them from rubbing and wearing out. is this true? if so is it soemthign i can get online or only from the dealership?

Airjam..that is one slick lookin ride. It's exactly what I want b/c I want x-cab but wanna keep the same color!! Guess I can't have my cake and eat it too.