Beagler Posted September 8, 2021 Share Posted September 8, 2021 Hi, anyone know what diff will be in my 2019 1.6 Sigma 270s Link to comment Share on other sites More sharing options...
K7 VCT Posted September 8, 2021 Share Posted September 8, 2021 Will be the BMW unit, unless upgraded. Link to comment Share on other sites More sharing options...
Beagler Posted September 8, 2021 Author Share Posted September 8, 2021 Thank you Link to comment Share on other sites More sharing options...
Beagler Posted September 8, 2021 Author Share Posted September 8, 2021 Have a whine that comes in at 50 on power, goes off on overrun or 60 mph on power Cant see it being diff at 11000 miles. Any ideas. Link to comment Share on other sites More sharing options...
ScottR400D Posted September 8, 2021 Share Posted September 8, 2021 It could certainly be the diff. They'll do that at any mileage. I'm sure if you contact CC they'll be able to fix it for you. ( ) Either that or they'll tell you it's normal and they all do it. Well, it is very common but they don't 'all' do it. Link to comment Share on other sites More sharing options...
Doc007 Posted September 8, 2021 Share Posted September 8, 2021 LSD or open? Link to comment Share on other sites More sharing options...
Beagler Posted September 8, 2021 Author Share Posted September 8, 2021 Rang CC and its a 3.91 BMW Open Diff whatever open means. Looking on the net its quite common. Anyone else have this issue. Link to comment Share on other sites More sharing options...
aerobod - near CYYC Posted September 8, 2021 Share Posted September 8, 2021 whatever open meansOpen means no Limited Slip unit installed. Link to comment Share on other sites More sharing options...
Beagler Posted September 8, 2021 Author Share Posted September 8, 2021 Thank you James. Link to comment Share on other sites More sharing options...
ScottR400D Posted September 8, 2021 Share Posted September 8, 2021 It's a 3.91 ratio (3.91 turns of the prop gives 1 turn of the driveshafts) BMW differential with, as said no limited slip. You have the 5 speed Mazda box which comes with a 3.91 diff. If it had had the 6 speed box it would have been a 3.64 diff because the 6 has a lower ratio top gear. Link to comment Share on other sites More sharing options...
Beagler Posted September 8, 2021 Author Share Posted September 8, 2021 Thanks guys. Link to comment Share on other sites More sharing options...
K7 VCT Posted September 8, 2021 Share Posted September 8, 2021 You'll get use to the various noises, it's part of 7 life, just wear ear plugs Link to comment Share on other sites More sharing options...
Beagler Posted September 8, 2021 Author Share Posted September 8, 2021 Does anyone elses do this. Link to comment Share on other sites More sharing options...
Benton Posted September 8, 2021 Share Posted September 8, 2021 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 Link to comment Share on other sites More sharing options...
Beagler Posted September 8, 2021 Author Share Posted September 8, 2021 Link to comment Share on other sites More sharing options...
ChrisC Posted September 8, 2021 Share Posted September 8, 2021 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. Link to comment Share on other sites More sharing options...
ScottR400D Posted September 9, 2021 Share Posted September 9, 2021 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. Link to comment Share on other sites More sharing options...
Nigel B Posted September 9, 2021 Share Posted September 9, 2021 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. Link to comment Share on other sites More sharing options...
Beagler Posted September 9, 2021 Author Share Posted September 9, 2021 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. Link to comment Share on other sites More sharing options...
ScottR400D Posted September 9, 2021 Share Posted September 9, 2021 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? Link to comment Share on other sites More sharing options...
Beagler Posted September 9, 2021 Author Share Posted September 9, 2021 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. Link to comment Share on other sites More sharing options...
Support Team andy_harries Posted September 9, 2021 Support Team Share Posted September 9, 2021 I have a 2016 Sigma engine with a 5 speed gearbox and BMW diff, so very similar set up to you and I wear earplugs due to the whine around 50mph. Have always assumed its gearbox whine. Link to comment Share on other sites More sharing options...
Beagler Posted September 9, 2021 Author Share Posted September 9, 2021 Thanks Andy nice to know its not only me. Link to comment Share on other sites More sharing options...
ScottR400D Posted September 9, 2021 Share Posted September 9, 2021 I wear earplugs because of the exhaust noise. And the diff noise. And the gearbox noise.........They are definitely normal! Link to comment Share on other sites More sharing options...
Beagler Posted September 9, 2021 Author Share Posted September 9, 2021 I just think anything noisier than the wife cant be normal Link to comment Share on other sites More sharing options...
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