Why does my diff bang and clatter?

[Andy Mac]

And can I stop it ? Can it be adjusted to give clearance? It's LSD.

Over bumps It does sound like it's knocking the chassis.

Also it whine's a lot on overrun. I know this is a thing we have to accept, but can I sound proof to reduce at all?

Thanks.

[Tazio]

First thing, 'sounds like banging on the chassis', check all the fixing bolts as they do come loose over time, and I've known the bolts to break.

As for the whining, there are loads of threads re different types of LSDs making loads of noises, so you'll have to add what car you have and what diff is fitted, Ford or BMW to help answer your questions.

[Andy Mac]

I believe it's a BMW LSD.

[Dan R]

You, as I have, will now discover the phrase TADTS 

[ScottR400D]

Which engine, bhp, how many miles, how old?
 

Is the diff bolted in properly?

[aerobod - near CYYC]

The bottom two bolts where the BMW diff mounts to the carrier can work loose and drop out, (I upped the torque on mine to 110Nm, added blue Loctite and kept the Schnorr washers in place and have since had no problems). Also, if you have an old style carrier that mounts at the top to the diff using two of the cover bolts instead of a long bolt through the top of the cover, the cover bolts can hit the deDion tube when the car is corned hard (there was an upgraded cover available in 2014 or so to fix that problem).

[Andy Mac]

That's good guys thanks. I think I need to get the car up and do some inspecting.

What about some sound proofing for the whining? Or am I being a bit anal?

[Benton]

What about some sound proofing for the whining? Or am I being a bit anal?

On the basis the overall noise level whilst driving a Caterham is already high (mechanical, exhaust, wind etc.) anyway if you don't already wear them then earplugs or headphones are recommended if you're driving for any length of time.

[aerobod - near CYYC]

With my BMW diff, the only noticeable whining is on the overrun in 4th gear (I have the 6-spd transmission), but no other whining above the exhaust note in other circumstances. I do run 75w140 oil that seems to help reduce diff noise, especially when the oil gets over 100°C, though.

[GulfSeven]

With an R it's only the diff housing that's BMW - it's a Titan LSD inside on the current cars which is a different beast all together. I think they all whine. Mine certainly does.

[ScottR400D]

The Titan is capable of making all sorts of noises, especially when it's on its way out. 

It's hard to give clear advice not knowing anything other than 'I believe it's a BMW' though. 
 

 

[Geoff Brown]

If you have check tightened all the attachments & there is no sign of fouling between back plate & de Dion then it has got to be the good old LSD. If it is a BMW ???

The banging & clattering is probably the backlash out of limits so that 'phenomena' is probably a combination of CWP & Titan.

There will be some whine on over run but if uncomfortably loud when taking the foot off the gas to decelerate from high speed - over 50/60 mph in 6th/5th - then there will be some mechanical noise.

A steady low pitched whine at set speeds, in certain gears & RPM can be attributable to either gear box or diff. But again if uncomfortably loud & from the rear - diff.

The Titan when lunching itself sort of screeches on cornering & when coasting at low speed to a stop, out of gear a low whine can be heard from the rear.

If you have a BMW LSD best to do the basic checks then escalate ! BMW Differential Titan limited slip unit - how to check & protect while in service. | Lotus Seven Club (lotus7.club)

To some degree TADTS is correct as there is a natural mechanical cacophony with a Sevens drive line BUT one should be able to disassociate the good from the bad.

Homework ! BMW/Titan LSD Viability | Lotus Seven Club (lotus7.club)

[Toughie]

Well done GulfSeven Tim.  I thought you were supposed to be a newbie.  Didn't take you long to get the hang of it.

[aerobod - near CYYC]

There won't be any whining due to the LSD when traveling in a straight line with no wheelspin, though, that will all be due to the gear mesh or bearings.

[Andy Mac]

Sorry gents. It's a 2017 420R with 6 speed

[GulfSeven]

#13 Yeah, well it's quite a steep learning curve once your Seven arrives isn't it! 

#14 Perhaps it's just gearbox whine on overrun then? I always assumed the whining was my LSD, but you're right, it's not specifically when cornering.

[ScottR400D]

How many miles OP? Any more than 6k or so, you're on borrowed time! 

[Toughie]

#16 Tim,

#13 Yeah, well it's quite a steep learning curve once your Seven arrives isn't it!

Hell, yeah!

[Mrp]

!

[Mrp]

Hi Andy Mac

Mine was exactly the same with less than 4K miles and is just about to have a Rebuild with a tracsport  lsd I think you might be in for the same. Budget for about £1475 + vat

mrp

[Tom_Arundel]

Caterham do/used to do, a stick on carpet kit that makes a difference if you don`t have one. I managed to fix my diff years ago but that is a long story!

[ChrisC]

My new build had terrible bang and chatter.  But its now all under control.  First I swapped the kit oil to Road and Race Transmissions specifically formulated blend.  Unfortunately it was as simple as that with my car.  By chance I was speaking with a 2021 spec kit builder, who asked where the gearbox spacer went, to which I replied what spacer.  It seem in 2021 Caterham introduced a spacer to lift the tail of the Mazda gearbox 3mm. This stopped 90% of my noises, which was suspected by Caterham themselves as diff noise, but obviously not.    This only applies to the 5speed, not the 6speed.

Sorry to say given the age of your car I would be checking the preload, and expecting a rebuild, unless you have a recent record of one. 

[john hooper]

Is this something that is available from cc online parts. I have searched but am unable to find it.

[Dixa1225]

https://caterhamparts.co.uk/fittings/7111-gearbox-mount-spacer.html?search_query=+3E0G0002A%29&results=1

[ChrisC]

It is, but your never find it, it has no image and is listed under *Seats and headrest fittings*.  Just search the part number 3E0G0002A.  It's £3.85, fits any 5 speed post 2013.  It fits between the gearbox and the gearbox mount, raising it by 3mm.  It can be fitted without removing anything other than the gearbox mount, I just supported the gearbox with a jack.  I believe the effect is most dramatic on Duratec cars, obviously I have only tried it in my 420R.