LSD again (sorry)

[StevehS3]

To save me ploughing through the mass of LSD information please can anyone help with the following relating to a 2017 310R

- which plate type is likely to be fitted and is there an obvious (visual) way of knowing?

- how knackered is it likely to be at 4,000 road miles - no track?

- is there a simple way of measuring the preload or determining its current state (sorry I've never touched a LSD before and I don't know the process)

- is there a Quaife option for the BMW diff that can be used as a replacement?

- what is the rough cost of the recommend SPC replacement if that is needed?

- is it a big job to replace it over winter? I am reasonably competent with the spanners but by no means a mechanic.

I am not being lazy, it's just there is so much info. Many thanks, Steve

[ChrisC]

2017 should have carbon plates, and yes they are likely to be warn out, or on the way at 4000.  Preload is simple to measure, 5 min task, you need a torque wrench and a 41mm socket (could be 42mm is the nut has been changed recently).  All it is, is the force needed to turn one wheel while the other is locked (on the ground). 
 

Yes there is a Quaife ATB for the BMW Diff, also a Drexler and the SPC.

I did mine in two weekends, one out, one in, the weeks before the fish and chip run.  Mine was removed for a prop replacement, not a diff issue.  Can't help on the SPC cost, but a Titan rebuild/reset is £150+vat, plus parts.

[aerobod - near CYYC]

An even quicker cursory test for the Titan LSD if you haven't got a torque wrench or socket to fit the axle, is to lift the rear axle off the ground and with the car out of gear, turn a wheel forward, the other wheel should turn in the same direction.

If this is not the case, the LSD definitely needs a rebuild, if it does turn in the same direction, then the test with the torque wrench to determine an accurate pre-load will give a better indication of LSD health.

[ScottR400D]

By all means carry out the checks but a 310 is likely to be OK at such a low mileage, IMO.

Analysis of the various threads leads me to believe that the Duratec 210/220 are most likely to overwhelm the Titan, particularly if coupled with the 6 speed box. 

Anecdotally, I have several mates with Sigma cars, 270s and 310s, all 2015/16 vintage with carbon plates and none have had problems at 15-20k miles. I have a similar number of mates with 210/220bhp Duratecs all of which have suffered failures between 3 and10k miles. 

When I had my issues, I was removing and refitting in 4.5-5 hours. 

[StevehS3]

Thank you very much for the replies. I will investigate and report the results.

[Mrp]

ChrisC's blog has a perfect set of instructions on the pre-load check Steve

That is  how I found out mine was Donald ducked

[Geoff Brown]

Instructions also here, available to all. BMW Differential Titan limited slip unit - how to check & protect while in service. | Lotus Seven Club (lotus7.club)

[K7 VCT]

Have a quaife ATB diff done at birds performance in Iver, bucks.

They've done a few 7s now.

Very happy with it, progressive and no maintenance ever.

Car is S3 310 no track work, all done in previous years of 7 ownership.

 

Message me for costs

 

 

 

[StevehS3]

Thank you so much everyone.

My usage will be a mix of track days and road. 

[StevehS3]

PM sent to K7 VCT

[7 wonders of the world]

why particularly with the 6 speeder - if anything this puts less torque through the LSD, possibly driving style is more influential

[ScottR400D]

No idea Neil, that's just how it appeared to be running over the cases I'm aware of. The 6 speeders seemed to fail at very low mileages. 

Maybe you're right and those with the 6 speed tend to be more 'agressive' or perhaps the torque is more consistently high because of the closeness of the ratios?

There are certainly a good number of 5 speed 420s that have suffered too. 

[Mrp]

Mine was a 5 speed and failed at less than 3k miles just to add to the question

[7 wonders of the world]

The 5 speeders produce more torque in 1st and 2nd, as the compound ratios are higher.

[Colin Heseltine]

Steve,

Have just checked the pre-load in my diff.  The car (a 420R new in April 2021) has done 5750 miles. Both wheels jacked off the ground they both rotate together the same way when one is moved.

Having just taken delivery of 42mm nut a few minutes ago, got out the fairly unused Halford Professional 3/8" drive torque wrench.  This has a rotating scale in 1ft lb increments. Starting from 20 ft lb went up in 5 ft lb increments till reached 35ft lb and then in 1ft lb increments. at 44.5 ft lbs I could not move the wheel at 45 ft. lbs it would move.  This would appear to indicate no problem.

I tried one of my other torque wrenches but was not happy with the way the scale was reading as it seem to move the wheel no matter what it was set to.  Think I will look for a further torque wrench for a second opinion.

Colin

[GulfSeven]

Good news Colin.

So if you have a 2021 420R, I assume my 2020 310R will also need a 42mm socket?

I'd be quite keen to be able to be able to test mine in the future too (although it's only done 2,300 miles so far).

[Colin Heseltine]

Have just purchased one of the Clarke digital torque wrench adaptors to use for a second opinion.  This appeared to move at 42.5 ft. lbs.  So perhaps if I take average of the two devices I am on 43.5 ft lbs.  Have also ordered the gold magnetic plug for the diff.  Perhaps if I check the preload every 1000 miles I will be able to see the deterioration (if any -  )

Colin

[ChrisC]

Above 42.5 ft.lbs. is all good, 20 is time to rebuild, assuming no other strange behaviour.  Just don't be fooled with those Clark digital torque wrenchs, mine showed a 10% difference between clockwise and anti-clockwise readings.  Not happy that this difference prompted my diff removal half way through the year, but it did ultimately lead to me finding my cars long term NVH issue, and just in time for it to be covered under warranty.  The advise I will give is just stick to one side for your readings with that torque wrench, so you can compare apples with apples next time you take a reading.

[ScottR400D]

I would also be aware that a deterioration is not necessarily going to happen gradually or consistently.  

Frequent checks are my advice, which isn't too onerous, it's an easy task. 

[eric]

Mine have about 50 000 miles mainly on the road , so never used :-)

[Golf Juliet Tango]

Thank goodness I use a bog standard open diff. It is just dandy and with 135,000 miles of use (or something close to that) it just isn't a problem.

Highly recommended.

[Nigel B]

There's just something about a LSD equipped Seven though.

There’s none of that ‘will it slide or will it spin up the inside wheel?’ nonsense you get with an open diff. 

You can control the car with pin point precision on the edge of grip, which for me is the whole point of a Caterham. 

I drove my first Seven for over ten years with an open diff, before progressing through Quaife, Titan & now Tracsport diffs, so I have quite a lot of experience with each type. 

I’d never go back to an open diff now, I think it would be very frustrating, from a driving perspective. In my experience, the Tracsport offers the best of both worlds. I’ve now covered over 7,500 miles with the Tracsport fitted & it’s just as quiet, unobtrusive & smoothly effective as when it was first fitted.

[David_B]

Hi, what is the reference for a Tracsport in a BMW diff ?

and really quiet as an open diff ? Thanks

[7 wonders of the world]

Speak to Steve here

https://www.tracsport.com/lsds

Yes, silent in operation as they should be, 

 

[Mrp]

Donuts are not really happening with an open diff, this is important