Sudden Whine in 1st & 2nd Gear (BMW Z4 E89 23i, Manual) – Need Expert Input

[TonyKTony]

Hi everyone,

I need some help diagnosing a sudden whining noise on my BMW Z4 E89 sDrive23i (N52, manual gearbox).

Symptoms:

• The noise only happens in 1st and 2nd gear
• Only between 1,000–2,000 rpm
• Only under acceleration / load
• Completely disappears above ~2000 rpm
• Cannot be heard revving the engine in neutral
• Appeared suddenly and has slowly gotten worse

Work already done:

• Auxiliary belt replaced
• Tensioner replaced
• Gearbox oil change

What the mechanic suspects:

• Possibly gearbox bearing noise (input shaft or secondary shaft)
• Or low-gear gear mesh whine
• Not engine, not belt/pulley related

 

[Z Victor 1]

What mileage has it done?

 

[TonyKTony]

What mileage has it done?

45,000 miles

 

[TonyKTony]

45,000 miles

The mechanic said that it sounds like the gearbox but not to overly stress as RWD cars are noisy. but to keep an eye on it.

 

[Z Victor 1]

Shouldn't be anything wrong with the gearbox at 45k !

 

[Duncodin]

I've heard differentials making a noise like you describe. Never heard it on a zed though - Maybe on a zed it might sound like it's coming from the gearbox because the diff is literally just behind you.

I've also heard it from gearboxes (again, not zeds) although usually it could also be felt through the gear lever, as if the gear lever was always resting on a balk ring - ie if the gear lever linkage wasn't lined up correctly - although most of my spannering experience comes from rear/mid engined cars where 'linkage' was always a nightmare.