Anyone had an X5/6M in drive on a hoist?

[CryptoHeff]

Hey there

I've been working with my mechanic to diagnose an odd sound that particularly happens when off the throttle and coasting in my F85. It sounds like diff clutch packs but happens in a straight line and I can replicate in any gear - particularly neutral if I need to make it do it on demand. The sound changes with the speed of the car (like something rotating and knocking) - but doesn't happen all the time and only when not under load.

We think it's potentially related to transfer case. To help us diagnose we put the car up on a hoist and in gear to drive the wheels and try to see if we could pinpoint the sound from underneath.

I turned off traction control and DSC. Oddly, on the hoist and in gear the front shaft didn't spin so only the rear wheels were spinning.

I was only applying throttle lightly and got into fifth gear at very low revs and speed with only the rear wheels turning.

Not sure if I then applied more throttle at some point, but the car made a bit of noise and jolted and then the front shaft and wheels started turning.

I wouldn't have thought this is how the car would have behaved on a hoist? Should all wheels have driven from pretty much idle in gear?

It does make us think that the issue is in the transfer case but thought I would check if anyone else has had experience with this/x drive and how it should behave.

Thanks.

[CryptoHeff]

Looking at this video, it seems like all wheels should have spun, so likely something not right with my car

https://youtu.be/Ze2KcWzYTiQ?si=f2JYZFQhSILS3rA_

[suitedcboy]

I ran my 50i on lift briefly and the front wheels turned slowly and traction message came on. I had not turned anything off. The video linked has no info so it may have reached an apply criteria like you found before the video started.
The AWD systems around with wet clutch T cases have varying strategies and some variation occurs on performance versions vs lower output engines. The general method is very low or no apply pressure on the clutches until engine torque rises, throttle apply rate is great, or wheelspin is detected. If the secondary drive (front end in this case) is applied in turns when unneeded then shudder or clunks are likely owing to speed differences of the 4 wheels and T case clutch trying to make the two ends of car go the same speed.

[CryptoHeff]

Thanks very much for the info. Definitely an interesting one. I guess I'll know once I get a chance to do a few more tests and get under the car again.