"Rattlesnake" noise after changing U-Joint

[Brown Betty]

Hey guys,

This morning I decided to take off my 1-piece driveshaft and change the U-Joints. Under hard acceleration I'll hear a "clunK", so I thought that the U-Joints may be the culprit.

With the driveshaft off the front U-Joint(Tranny) seemed to be in great condition, so I left that one on. The rear one(axle) was stiff, so after fighting with it for over an hour I got the U-Joint changed Now, this new U-Joint is VERY STIFF, but I still put the driveshaft back on the truck.

I took the truck out for a spin to see if the "clunk" was gone, but it was still there And now whenever I accelerate my truck sounds like a rattlesnake Or a Maraca... Your choice

Any ideas guys? I'm guessing it has to do with the U-Joint being very stiff... But I'm stuck there

Thanks,
Darcy