Drivetrain whine
 

2010 X5d with 140k miles.

I've picked up a high pitch whine. It only happens when moving and changes with gear shifts. My girlfriend even noticed it cruising down the interstate at 80mph. Just ordered BMW transfer case oil and I don't know if or when the lifetime transmission fluid was changed. Anyone go through this?

If it changes with gear shifts then it is either transmission or engine related. Transfer case is pegged to road speed and won’t change with gear shifts. Having said that, I would recommend you service all the driveline fluids:

- front and rear differentials: 2 quarts total 75W-90 synthetic
- transfer case: BMW TF 0870 or Shell S-Tec (same fluid, slightly cheaper)
- transmission: ZF Lifeguard 6 (12 liters to do two pan drops) + ZF pan/filter

I (and others) have had success with other transmission fluids (Pentosin ATF1 in my case), such as Mercon SP. I’ll leave that up to you.

Thx,
That's the route I will go. My son is a tech at a dealer so i get parts/fluid for cost +10% so that makes parts buying easy. Also, just went on a 2100 mile road trip and it performed great.

Whine is usually the pinion bearing. You would need to run on a lift and probe it with a stethoscope to be sure. It is not going to leave you on the side of the road but they can be annoying. Our E53 makes whine at certain loads. Give it more or less power and it goes away.

there has been the odd rear diff failure. Do a search here and on bimmerfest E70

Thanks for the replies. After a little more diagnostics I gave you bad info. It turned out to be the tensioner or pulley. Not sure which I just ordered both and belts. It's so quiet now it's almost eerie.