99 hilux 4x4 clunking in rear

If it is just the one or two clunks it could be a universal on the rear drive train that is need or greasing or replacing.

Phil

Could be a number of things.
I would start by checking how much backlash is in the drive train. To do this, check how much you can twist the prop shft by hand from one extreme to the other. That will help isolate the problem but still won't tell you whether it's a worn uni joint or excessive backlash between crown wheel and pinion (in the diff).
The other thing might be worn suspension bushes, dragging brakes/handbrake, loose spare wheel....... the list goes on.
Time to get your hands dirty me thinks!

Fab.

As well as checking above drive shaft issues grab the shaft & check for excessive
wear in the carrier bearing, in the middle of shaft...will be very obvious if crook.
.....oldbaz.