Grinding on bumps and with heavy load

Howdy. First time poster.

I am a landscaper and have used my Manual trans, 2.7 2WD to transport mulch and moderate amounts of material (500-1000lb) for years.
Recently when I have loaded her with even a modest amount of weight (400lb or so) I am getting a pretty gnarly grinding sound when accelerating but ONLY when the truck bounces after a speed bump or pothole.
However, if the truck is fully loaded, lets say with 600 or more pounds (yard of mulch etc) it grinds the whole time. Like pull over on the side of the road and dump the cargo or face catastrophe style (not that I did that or anything .)
I thought maybe differential, but it's only when the truck has a heavy cargo. When I drive her on the road, I can floor it and don't get the grinding so may rule that out. Diff oil level is good and clean.
My other thought is the drive shaft is making contact with the body somehow when a heavy cargo is loaded. Thus when going over a bump with a load, truck bounces onto the drive shaft temporarily.
So bad shocks? Is it even possible for the body to make contact with drive shaft? I've gotten under there when truck had a load and couldn't see any contact.
Grateful for any expertise y'all may have.

 

Welcome to Tacoma World. Do you still have the OEM leaf springs? Have you ever services any U joints or carrier bearing on the driveshaft? How many miles on the truck?

I'm going to make a wild guess that if it's sagging down the rear end badly from worn out leaf springs, your driveshaft angle is getting pushed past the point of being happy and grinding U joints or something like that. Hopefully it's not something worse but you'd have to crawl under there and take a look (or take it to a shop if you don't know what to look for).

Probably time to refresh some suspension and driveline components. Good luck.

 

Hey. Thanks for the response.

The U joints have been replaced 2 times: 6 years ago and last summer (2022) and the truck has 170k on her.

I took the truck back to the mechanic who replaced the u joints recently and told them about this grinding. As I did not have a load in the truck at the time we could not hear anything. I left it with them and they said they couldn't discern anything. "Bring it back with a heavy load in it sometime" they said.

For what it's worth, the leaf springs were under recall and I had them replaced maybe 5-6 years ago.