Thumping sound from rear at 45 mph on 1990 Nissan 300ZX

Just bought the car and on the third drive it made a thumping sound at 45 mph that only lasted a second or so. Didn't make the sound before 45 mph or after. Sounded like it was coming from the rear. Haven't driven it since. Drove it twice before and it didn't make this noise. (kind of sounds like when you run over the rumble strip on the highway). Thx.

Asked by for the 1990 Nissan 300ZX
Sounds like a wheel bearing or a bad tire , switch the tire with a front one and see if the sound moves to the front , and while you have the rear tire off check the bearing in the rear by spinning the hub and using a stethoscope to listen to see if you hear the same kind of noise , hope this helps , Kevvs
Also check to see if you have gear oil in the rear end
1 more answer
While the car is on jack stands, check the drive shaft center bearing and U-joints.
Also, check the condition of both halfshafts/axle shafts.