Orange is my new black
Does anyone elses do this.
2019 270S 1.6
My old 420R (Bmw) diff used to have a pronounced whine at 60mph, 5mph either side the whine disappeared. Did it from new.
Current 620R (Sierra) diff probably whines as well but you cant hear it above the sequential gearbox noise
Oil plays a part in whine, the historic posts in blatchat proves that. The latest Caterham oil partners diff oil offering maybe isn't the quietest, so I am confident a quieter oil could be found, but what would be the question.
There are plenty of posts about Ford diffs and oil choice, not sure about BMW units. Just don't get confused with LSD oil, which isn't needed for an open diff.
My detailed build blog
I've tried a few different oils in my LSDs and not seen any noticeable difference in noise levels.
Having said that I've not had a noticeable 'whine' just all the other normal noises.
Recently I was in communication with a member who had what he described as a horrific whine which was improved by adjusting the side bearings, which seemed to imply that the whine was caused by incorrect setting of the CW and P.
I had a speed related whine from the diff on my last Caterham that sounded very similar to what you’re describing.
It turned out to be caused by an incorrectly adjusted crown wheel and pinion. I sent the diff to Road and Race Transmissions who adjusted it. It immediately sounded much quieter and became progressively quieter still over the course of the next couple of thousand miles.
Spoke to a really nice guy at Road and Race Transmissions and he said what I describe is unlikely to be from the diff internals but resonance emanating from the diff due to the way its mounted. He also said something interesting. The gearbox noise on idle that goes away when the clutch is depressed is for the most due to the state of tune of the engine and it pulsing causing gears to backlash together. Although he said he would look at the diff, in his opinion it was not faulty.
The effect you mention of gearbox noise caused by the engine firing pulses is a fairly widespread theory and I'm told is likely responsible for the 'chatter' of the CW&P on very light throttle openings which many of us get.
The effect is supposed to be more noticeable with a lightened flywheel. Does your 270 have that?
No it doesn't. I remember the Westfield I built had the noticeable gearbox rumble on idle the same. I think also as your sat next to the gearbox with no real sound deadening its all quite exagerated and normal.