Popping sound when accelerating

[E53Envyy]

Hi guys,

As a continuation from my previous thread on CV-axles this new thread will be specifically on the popping issue.

Lets recap:
- An occasional popping issue started to arise a couple months ago under hard acceleration.
- This popping sound became more and more frequent, and seemed to be more prominent when turning left. This lead to my CV-axle thread as I was pretty sure it must be the CV-axle.
- Before replacing the CV-axle I removed the front driveshaft and check the splines, Looked good (refer to photo below). I greased the splines and reinstalled the driveshaft.
- I installed new Cardone axles along with diff output shaft seals and fluid. The fluid may have been a little low and definitely needed replacing. Someone else had been messing with the axles before as the old ones slid out of the hubs with ease. The old axles also had GSP stamped into the boot clamps (would this indicate the old axles had been replaced at sometime?). Also, the old axle boots were intact without tearing or cracking.

The popping sounds persists!

To eliminate the possibility of non drivetrain components I disconnected the transfer case servo motor. This prevents the transfer case from sending power to the front wheels... no more popping!

So we know:
The sound is coming from the front drivetrain.
The front CV-axles are new (but could somehow already have failed... unlikely but I'll keep that as a possibility)
The front driveshaft splines show no sign of slippage and the overall driveshaft assembly looks good (flex disk etc)
The splines on the front hubs look good and no signs of slippage
The splines going into the differential look good and no signs of slippage
Note: Since this is a facelift X5 I cannot have a failing transfer case chain, I believe that was specific to early model X5's

What can we conclude?
The differential and transferase are the unknown in this situation. Maybe a failure of a differential gear is the cause. Unless anyone has any other ideas I'm going to try to remove the differential cover (hopefully that's possible without removing the diff) and check the gears.

I've also taken a quick audio clip of the noise, I'll try to upload it soon. It sounds similar to this video but not quite as high pitch and not as frequent. It actually reminds me of a stripped differential in a scale RC car.

Driveshaft spline:



Cheers, E53Envyy