Knocking sound in rear. 2wd

Hello, first post here but i've been skimming for a while for repair stuff.

I have a 2001 Tundra limited 2wd i bought for 3k. Couldnt drive over 20 mph.
Changed the following:
-Drive shaft and carrier baring
-Brake booster
-Wheels and Tires
-Front suspension
-Rear is getting changed soon!
-Spark plugs and ignition coils
-Front brakes

The person i purchased it from said it had a welded diff, i drove it on the beach after changing a lot of the stuff and it got stuck(2wd) and once we got it out the rear end started the clicking. I can drive now but i have a clanking sound in the rear axle any time i am rolling. Sounds like it clicks at the speed the wheels are rotating. I checked the drums and everything looked fine. I've been hesitant on opening the diff and checking it as affording a rebuild is not likely.

Anytime we shift to drive from reverse or vice versa you can feel the wheels knocking into place and then it goes, as well as when driving down the highway if you take your foot off the gas to roll and then reapply gas you feel a jolt like it is reengaging.

Was wondering if anyone has any knowledge on this or can point me in the correct place to look.

Spouse and i are both thinking the "weld" broke and took some teeth with it or the pinion gear is bad.