Clunk Clunk u Joints?
 

Before I spend $500 at Mazdatrix on a new Aluminium drive shaft I would appreciate opinions of other readers of this forum. Two weeks ago pulling out of a driveway I noticed the sound clunk clunk coming from the rear, a couple of days later it then started when going forward too. It only happens when the drive train is not under load. I should also mention that there is no vibration and there seems to be 2 clunks for each wheel rotation. Because it started when only backing up I assumed it was a bad u joint. Then jacked the car up took the trans to diff brace off and the u joints only had a little play, barely noticeable but it does have some play. Maybe a cv joint but I am under the impression the rear drive Mazda cv joints rarely go? Also checked the rotors and they are perfect. Of course with the car on jack stands there was no sound when the rear wheels are spun either by hand or under power. I should also mention that it is a 06 Shinka with 45k miles and is driven rather briskly. Any opinions will be greatly appreciated.
Thank you

Never heard of our u joints going that early but it could be . There shouldn't be any play in them at all . Why not just buy a second hand carbon fiber shaft for way less $ ?

Update, clunk went away even from forward to backwards but now I get a bad vibration above 50 mph has to be the drive shaft/ u joints. Ordered a used one from ebay with only 15k on it. Although I wonder why Mazda charges $1100 for a new one and used ones go for $80 to $200

Solution, I almost did't post this. I was a mechanic for 17 years and involved with race cars for 25 years. I'm guilty of over thinking the problem of clunk. After raising the car on jack stands for the 4th time trying to diagnose the cause, I was spinning the rear wheel by hand and felt a protrusion on the tire and found a a brand new 13 mm nut stuck in the thread in fact I found two, one on the opposite side of the tire also. Pop them out and now everything is alright with the world. Talk about brain fade. Luckily I didn't order the drive shaft. Spent almost 3 weeks trying to figure this out. Trying not to hang my head in shame.

no worries man .......It's so easy to get tunnel vision when problem solving .