You may have U-Joint problems
It shouldn't ...
check engine mounts
U joint
check the fluid in the rear end it might be dry causing medal to grind causing a clunk noise or the gears in the rear end or worn done causing it to do the same thing
You're a clunk-head...
Need to check the rear u-joint in the drive shaft.
Check driveshaft center bearing Check 'U" joints Maybe transmission mount
Pull the rear wheels off and check the brakes. Something may have broken or fell apart.
Vrrrrrrroommm If the driver puts his foot down. Brrrr-clunk-rrrrr-clunk-rrrrrrrrr With added gear changes.
A centipede with a wooden leg
If the clunk is most noticeable at takeoff or when coming to a stop, the u-joints on the drive shaft probably need to be replaced.
May be as simple as needs the oil topping up in the gearbox