Popping sound when accelerating

[E53Envyy]

Yup it was the chain popping! With a simple tensioner it would’ve been fine for another 100k kms as all the internal bearings and clutches looked brand new (it had 270k kms).

Here’s a look inside:



Unfortunately the “new” transfer case is leaking from the rear output shaft at the guibo. Most likely the o-ring since it’s not running down the outside of the case but instead dripping from the guibo. It’s never easy lol




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[Ashaman074]

Just wanted to say how much I appreciate this post in 2025! My 2005 X5 has the same popping sound; and I have been baffled as to where it is originating from. I performed the same initial steps as you, with the same outcome; only to have the sound continue. Looks like I will be ordering a new transfer case chain soon... Thanks again!

[E53Envyy]

Originally Posted by Ashaman074

Just wanted to say how much I appreciate this post in 2025! My 2005 X5 has the same popping sound; and I have been baffled as to where it is originating from. I performed the same initial steps as you, with the same outcome; only to have the sound continue. Looks like I will be ordering a new transfer case chain soon... Thanks again!

Great to see this post is still useful! Was definitely one of the more difficult issues to find. I picked up an e83 X3 and shortly after it started doing the same thing so I guess I’m just cursed. Unplugging the actuator is a good solution if you don’t need 4x4 (and I think it slightly helps with fuel efficiency).

Also, never had an issue with the Cardone axles

Cheers

[80stech]

I'd wonder if anyone has changed the oil and not used the right oil. Usually it's the oil that will stretch the chain more than the load, especially in colder climates. I doubt if any oil change places, who are always promoting changing as much as they can, are using the exact right oil.

[E53Envyy]

Originally Posted by 80stech

I'd wonder if anyone has changed the oil and not used the right oil. Usually it's the oil that will stretch the chain more than the load, especially in colder climates. I doubt if any oil change places, who are always promoting changing as much as they can, are using the exact right oil.

I could definitely see people using the wrong oil as the OEM stuff (DTF) is extremely expensive for what it is. Although I thought that’s specifically for clutch life, not sure how picky the chain would be. The main issue is the lack of a tensioner, I would say it’s planned failure and I’m very disappointed in BMW for doing that. As I said, same issue in the X3 and is even more common (roughly half the E83’s that are being parted out are due to transfer case issues). Even the F15’s have this issue and I bet the G05 is the same design.

My snowmobile from the 90s has a tensioner in the chain case plus a dipstick with a magnet on the end. It’s designed to last, and takes simple gear lube. Would be nice to see new cars have the same attention to longevity (to be fair, BMW has done a great job on the B series engines in this regard).

Cheers

[80stech]

Having a tensioner would just be a band-aid, as was pointed out earlier, wear on the sprockets (and noise) would be the trade off for a few more miles. Either of my high mileage vehicles have had this issue (YET! and my wife's E83 transfer case had only an ounce or two of oil in when we bought it. Not only is the hydraulic pressure of the oil on the chain a problem, if the clutches don't have the right coefficient of friction, maybe some different size/wear issues on the tires, that all adds to it.

Try replacing the gear lube in your snowmobile chain case with low temp lubriplate and you be shocked at the difference it makes

[E53Envyy]

Originally Posted by 80stech

Having a tensioner would just be a band-aid, as was pointed out earlier, wear on the sprockets (and noise) would be the trade off for a few more miles. Either of my high mileage vehicles have had this issue (YET! and my wife's E83 transfer case had only an ounce or two of oil in when we bought it. Not only is the hydraulic pressure of the oil on the chain a problem, if the clutches don't have the right coefficient of friction, maybe some different size/wear issues on the tires, that all adds to it.

Try replacing the gear lube in your snowmobile chain case with low temp lubriplate and you be shocked at the difference it makes

Hmmm I would think the additional wear on the sprockets and noise would be minimal. For example, the valvetrain in the M54 has two tensioners and is considered to be very robust (obviously a very different application but figured I’d use a BMW example). The lack of a tensioner is probably due to cost and size. Seems like most manufacturers designed their t-cases the same way and all have the same fault. Just happens when you’re outside the warranty period and the chain is considered a wear and tear item.

Is lubriplate a type of grease? Lol not sure how well that’d work.

[80stech]

Again, it's not the tensioner that would add wear, it's the stretched chain. You are thinking about it in the wrong way.

[E53Envyy]

yeah I understand that once the chain has stretched the sprocket mesh isn’t within tolerance. The tensioner would help remove backlash and extend the life of the chain (in theory). Would be interesting to see a comparison. But you’re right that simply slapping a tensioner in there after it’s stretched won’t do much as the wear is already done.