First post here. Recently picked up a 1990 4runner, running and driving for $1600. anyways there is this intermittent rumbling sound. it happens above about 20kmh and stops around there too. it is somewhat affected by speed. in 2wd it happens during accel, coasting, decel. in 4wd, only during decel. not really sure what to make of this, but it doesn’t sound like a wheel bearing. any help appreciated. Thanks in advance. will be greasing everything with a zerk and checking diff fluid levels tomorrow.