Hi All,

73 240Z 5 speed WR, R200 and ZCG CV axles (no U joints on the shafts) 

Experiencing thumping / vibration sound from mid to rear of the car at 45+ MPH and the thumping/ vibration sound gets more rapid as speed increases.

Leaning towards the drive shaft U joints? under the car for inspection, rotating the drive shaft there appears to be play/slop not sure if this is normal?

Any other test to determined if the DS U joints are compromised? Both joints have zerk fittings and are well greased. 

All other components in the rear have been replaced in the past two years, suspension bushings, wheel bearings and seals, R200 rebuilt, new diff mount, mustache bar bushing, springs, struts, brakes, wheels and tires.  

Thank you.

 There shouldn't be any detectable slop in the u-joints in any direction.