2018 Diff clunk

[CtrMint]

Guys,

I'm raising this thread with some degree of caution, partly as I'm probably being paranoid but also because it is going to be rather difficult to offer precision in terms of an assessment etc.

Having got my 7 on the road last Friday I am surprised just how loud the clunk is from the LSD when taking up torque, and it's particularly bad in reverse.  The diff is nice and quiet once loaded with no whine etc so it seems fine, it's just disconcerting to have such a noise from a road car, I appreciate these aren't normal road cars.  The noise is similar to the LSD I've experienced when rallying in cars such as Evos and Imprezas.  My experience there is as a co-driver, so please don't assume any mechanical knowledge :-)

I've jacked the car up and taken a look, everything seems tight but there are a few degrees of play before the take-up, I think the term is backlash.  Not sure on the exact measurement, but I'm comparing the rotation of the wheels whilst jacked.  The prop and prop UJ seem secure without play.

Unfortunately, the earliest date I can get the car to Oakmere is the 30th April, and I'd love to be able to drive it.  I'm wondering if anyone has any simple sanity checks I can perform?  If this was the noise from the rear end of Evo rally car I'd expect it, it's just unnerving for my shiny new 7.  I also didn't experience this when I drove Oakmere's stock 620s.

As an aside, while nosing this evening I did spot the prop UJs had expelled a lot of grease up the side of the chassis panelling both front and rear UJ.  Is that normal? I've never even greased or assessed a prop before the build, so I'm totally in the dark with that too.,

I appreciate this has probably been asked before, I guess I'm just looking for piece of mind before I can get the car to the mainland.

Thanks,

Mark

[SM25T]

The grease is just from the UJs being over-greased .... it gets flung off the joints as the prop turns.

[Mark w]

I suspect its "normal " .

With the diff bolted solidly in the chassis right next to the driver and lack of any sound deadening any noise tends to get amplified.

Get it checked out but i suspect your OK to drive it in the interim . 

[Petethediesel]

My new 360 has the latest spec sintered plate lsd and certainly displays a good "clunk" on torque reversal. As mentioned previously, it is solid mounted, so inevitably noisy.

 The grease splatter is normal, most of us will add more grease than is actually needed when pumping  at service intervals to be sure it's at the max. Consider it chassis corrosion protection!

  I'd be confident to drive it and wait for the check at your dealer come 1000 miles..

[ECR]

It's the thing that most worried me on my first drive but it's normal .....

[CtrMint]

Thanks all, 

Do you think there's any sanity checks i can carry out?

Also is there a break-in period or procedure for the LSD?  The users manual only mentions running the engine in.

[7 wonders of the world]

Sorry to disagree but whilst it may be a normal characteristic fo the Titan LSD - CC current choice of LSD supplier, it is not normal for the like of ZF, Tracsport etc whose design is considerably better.

 

[CtrMint]

are you saying there is likely to be a problem?

[Tazio]

Just drive the bloody thing, it's just one of those 'normal' 7 foibles, and learn to stop listening for creaks and bangs, just use better hearing protection.

[Collidog]

I get no harsh noises from my LSD (2018 420). 

Plenty of creaks from the car though. As said above, decent earplugs smooth this out

[CtrMint]

Shot a video of it.

[Tom_Arundel]

I presume the diff is full of the correct oil

[CtrMint]

Yeah it's got the supplied oil in it.

It seems ridiculously harsh, and metal on metal.

[7 wonders of the world]

Not sure what oil CC currently supply but they used to use a straight grade final drive oil along with a sachet of lubegaurd to be added to vehicles fitted with a plate LSD, of course they may now supply an LSD compatible oil ?

[CtrMint]

I was supplied with Motul SAE 75W140 100% Synthetic gear oil for LSD.

[Jim 123]

In your video it is difficult to evaluate as the car is in neutral and the diff is rotating as you simulate the clunk.  Do you have any idea what travel or angle of movement you are getting in one direction when the diff flange is locked?

[Geoff Brown]

A good *75w/140 is the correct oil for the BMW LSD - I found that out the hard way due to the fact that the Caterham build manual & oil spec info was way behind the build spec in 2012. EP90!

Unfortunately "they all do that sir". It is just a foible of the vehicle. When something is about to let go you will know in no uncertain terms!

Remember that the LSD is to a certain extent on solid mounts & that 18 gauge aluminium is not the greatest sound barrier in the world especially when your backside is millimeters from the hot spinning lump.

After three Sevens one gets immune to the usual sounds of everything spinning & whirring but it is the odd low resonance buzz that can get up your nose until you track it down.

* Maybe I should have stated that the correct oil is 75w/140 LSD as in Castrol Syntrax 70w/140 or MOTUL GEAR Competition 75w/140 Racing Fully Synthetic       LSD

 

[7 wonders of the world]

Not strictly correct Geoff as normal oils do not have the extra 'slippery' additives needed to help reduce the 'chatter' of the plates in a plate LSD most noticeable on full lock at slow speeds forward or reverse. Plain grade oils will need the lubegaurd type product adding.

This does not apply to Torque biasing units for either AP Suretrac or Quaife 

 

[CtrMint]

Is the oil correct?  Do I need something additional?

 

[CtrMint]

Jim,

I've put the car in 1st and held one wheel, the amount of movement is reduced along with the volume of the noise,  where would you recommend measuring the travel?

Putting the car in gear has also shown some noise is also coming from the front side of the prop, I guess I should have been more liberal with the grease on the splines.

[aerobod - near CYYC]

If it is this Motul https://www.motul.com/be/en/products/gear-competition-75w140 then it is totally suitable without any additives. I use Redline 75w140, but there is some clunking. The LSD plates may also need a bit of bedding for smoother operation.

[ChrisC]

Motul 75w140 is recommended by Titan (the manufacture of your LSD) and 75w140 is recommended by BMW so I would think that covers it.   

[7 wonders of the world]

The plates would not cause a clunk or knock - bedded in or otherwise, they will creak or chatter, noticeable at low speed and maximum wheel speed variation ie on full lock, if you are truly hearing a clunk this is more indicative of excessive movement in the LSD pack as torque is applied and removed.

The Titan design has suffered from failures of the Belleville springs due to in no small part to their chosen design, 

However you do need to ascertain if indeed the LSD is the source though as there are many other areas in the transmission capable of causing such a noise, at least 6 sets of splines, UJ's etc.

Not to mention the normal gearbox location in the tunnel etc etc, components touching chassis, sounds in a Caterham are very easily transmitted to other parts of the car along the tubing often taking you down a dark diagnostic alley.

If as you say it sounds metal on metal I would be looking for witness marks in the transmission tunnel and engine bay to start with.

[CtrMint]

There is some noise from the front end of the prop, but it’s only minor.  The majority of the noise definitely originates from the diff.  I don’t think it’s from the chassis as I can create the noise whilst the car is jacked up and rotating the wheels a couple of degrees, so there’s no lateral load etc.

I have put as much force on the UJs as I can and they are rock solid with no lateral movement, I basically can’t moves them, other than rotate the prop.  I’ve also,greased them again just in case.

[Tazio]

I can't believe this thread is still being fed, some of the posts feed the OPs anxieties as a new owner. Get in and enjoy, spend less time on here, spend more time in the car, the noises, the clunks are normal. I have a ZF slipper diff that had 4 years racing, 7 years sprinting, it clunks, oh does it clunk...doesn't stop me from enjoying the drive.