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

[andrewwynn]

Did you take a picture of the inside of the transfer case? The splines slip because the drive shaft is too short there doesn't necessarily have to be wear on the male side (though it would be strange).

When a CV pops out you usually get loss of drive at all with e53 but if you have x-drive than the TC would likely stop sending torque forward. Check your CV axles fort full insertion into the dif

The sound in the video is the front drive prop skipping in the TC

[E53Envyy]

Originally Posted by andrewwynn

Did you take a picture of the inside of the transfer case? The splines slip because the drive shaft is too short there doesn't necessarily have to be wear on the male side (though it would be strange).

When a CV pops out you usually get loss of drive at all with e53 but if you have x-drive than the TC would likely stop sending torque forward. Check your CV axles fort full insertion into the dif

The sound in the video is the front drive prop skipping in the TC

Thanks, Regarding the transfer case, everything looked good. If it was slipping there I’d have seen shinny metal flakes. I did double check the transfer case before reinstalling the driveshaft. I’ll double check the output shafts of the diff. When I hear the popping I don’t feel a power loss or the effect of xdrive kicking in so it’s hard to say.

Thanks for the input, hopefully I’ll figure this out shortly.

[ahlem]

Did you support the front end and rotate the wheels by hand while in neutral? Maybe block one side and rotate each separately to see if anything side specific shows up? Could possibly be a wheel bearing going bad.

[andrewwynn]

Bearing won't pop but outer CV sure will.

A softer version of drive prop that happens when tuning left can easily be a binding/releasing CV joint.

I believe you said they are new but new ≠ fixed. Get a recording of the sound.

[X5chemist]

Are steering components up to par? I've heard ball joints pop under pressure. Xdrive does put pressure on them.

[E53Envyy]

Here is the video. Not too long of a video and the audio quality isn't the best but I think you can get the idea. I was driving straight on a slight hill with max 2/3 throttle. Oh, if you listen closely you will hear some belt squeal which is now fixed.

@X5chemist The inner/out tie rods are brand new Lemforder. The issue started before I replaced the tie rods and continues to happen afterwords.

Just to reiterate, after disconnecting the transfer case motor/servo the sound stopped even under full throttle. When the tcase motor is connected the popping/clicking starts.

Thanks guys!

[andrewwynn]

It does lean more towards thunk (CV joint) than tink (drive shaft spline). Did you say both CV axle new?

[E53Envyy]

Originally Posted by andrewwynn

It does lean more towards thunk (CV joint) than tink (drive shaft spline). Did you say both CV axle new?

Yes both CV-axles are new! Now the interesting point I could make is, the frequency of the sound before and after is practically the same. Where replacing the axles didn't have an effect...

[ahlem]

Any loose plastic parts blowing in the breeze under there? Any fender liner parts loose?