Have a 2001 Z71 with 250k miles. Original rear end. Starting clunking lately when down shifting (automatic). Loud enough to notice, but had not heard before. Jacked up the rear, put on stands, put it in drive, let up on brake, and driveshaft free spun (no wheel turn), then a loud clank and started moving the wheels. If I braked to stop the wheels from turning, and then let up on pedal again, same loud clank coming from rear end.

Couple days ago while driving it, if I accelerated quickly, the first few seconds sounded like a scrapping noise, or almost like a piece of wire wrapped around the driveshaft slapping the back end. Once I was going faster, it would stop. Also, made the same noise when coming to a stop. Friday it got pretty consistent. Drove it home and parked it.

Getting ready to drain the fluid to look for metal. Any suggestions/thoughts would be greatly appreciated.

Thanks,
Dave

 

UPDATE: Fluid was good. Nothing wrong with rear end. The problem was universal joint from driveshaft to rear axle. Of the four cups, one had the rubber seal letting loose and inside cup rusted out. The stock u-joint did not have zerk fitting. Stock original lasted almost 15 years. Quick $15 fix. Dropped driveshaft and changed out the u-joint with one that can be greased. Fairly easy to do with hammer and socket. Now I know the odd sound I was hearing. Also, do not trust reaching up and shaking the driveshaft. With three of the four u-joint ends still fine, it was the one that made the odd noise when accelerating and coming to a stop. Needed to get up close to see around each cup to even notice the one.

 

Good find - u joint was my 1st guess