'11 Silverado bed knocking under load

[zeal]

Went out camping last year and almost high centered on a rock, sounded like the bed busted loose but after looking under the truck for a good bit nothing seemed damaged or out of place. Now I'm noticing anytime I have more than a couple hundred pounds in the bed I'm hearing a knocking sound anytime I turn left or go over bumps/rough road. Sounds like it's coming from the back of the cab or front of the bed but I can't really identify it. Any help would be appreciated.

[Bad Bowtie2]

Quote

When was the last time you checked the air pressure in your spare? 

Is it still nice & tight under the bed?

 

[Sharpz]

99 percent chance its your U-Joints for your main drive shaft, probably at the tranny side.  W/ the truck in neutral, and wheels blocked get under the truck and check for play.

[zeal]

8 hours ago, Bad Bowtie2 said:

 

 

Spare has good pressure and is secure.

 

4 hours ago, Sharpz said:

99 percent chance its your U-Joints for your main drive shaft, probably at the tranny side.  W/ the truck in neutral, and wheels blocked get under the truck and check for play.

 

I did notice shifting R>D with my foot on the brake I get a knock sound and the truck jumps a bit. I will check for play when I get home, is it supposed to be free at all or should I not be able to move it? Haven't done u joints before. Also if that's the issue is it good practice to replace all 4 at once or just worry about the fronts?

Edited May 5, 2021 by zeal

[Sharpz]

clunking between reverse and drive is a good indication of u-joint wear.  Idealy you would change all out at the same time, same as wheel bearings and cv joints......... but the front shaft probably in reality will go twice as long as your main shaft, and that is the one you should focus on.  Obviously check all when under the truck.

[zeal]

On 5/5/2021 at 4:44 PM, Sharpz said:

clunking between reverse and drive is a good indication of u-joint wear.  Idealy you would change all out at the same time, same as wheel bearings and cv joints......... but the front shaft probably in reality will go twice as long as your main shaft, and that is the one you should focus on.  Obviously check all when under the truck.

 

Got everything swapped out yesterday, haven't had a chance to load up the bed yet and see if that noise is gone but I still do get the clunk when shifting into D. Doing some more research seems it may be an issue with the slip yoke needing lubed so I'll yank it off again to do that real quick. Thanks for your help, it's appreciated!