my 98 just recently started doing this when i am under hard brakeing or accelerating right when the body first move ie the front end comes up or down i hear a light pop from the rear somewhere i have checked all the bolt on the suspension and they are all tight. secondly when i launch off the line the rear end fells like it hits the floor and moves but once again i checked the torque arm it is tight i also checked out the inside of my diff when i changed the fluid no broken teeth everything is good. i was thinkin mayeb the u joints cuase sometimes when i am driving at slow speed ie u turns if i come around the corner when the tranny is still in first and i get off the pedal right before it trys to shift into second you can hear a loud metal to metal thud under the car. sorry this is so long but i cant figure it out.

 

TRANS MOUNT. IF THE NOISE HAPPENS WHEN UNDER HARD ACCELERATION OR WHEN IT SHIFTS

 

just at first instance when the body moves it seems to do it when the rear suspension flexes cause i have heard it do it in turns also.

 

examine rear springs for breaks