Suretrac LSD

[ben7]

Ok ok, so I've trawled through previous threads on noisy lsd's and concluded that TADTS.

 

I've just fitted one of the above on my current car having previously owned a se7en for several years with the same type of unit fitted. I'm familiar with the shunt related 'knock' when applying power and the general whining etc. As you say TADTS.

 

The problem I'm having here is a very significant clunk when on full lock/going around a roundabout/manoeuvring around a carpark. Apart from sounding dreadful, it's accompanied by a (or usually a series of) significant jolts, resulting in the backend lurching out.

 

It feels like something mechanical is trying to climb over something else - to explain it, it is a cross between a UJ over extending itself (IYSWIM) and the feeling I got when the rubber driveshaft boots wore out on the front my old pug 205 all those years ago.

 

As I say, I've previously owned the same set up and driven plenty of others with the same unit as well, so it's certainly not normal.

 

It's occurred as a result of fitting the lsd unit into the diff and then the car. So it may not necessarily be the lsd itself, but something that was moved when the old diif was removed, lsd fitted, then the whole lot put back together again????

 

Help please

 

Ben

 

Edited by - V500OSV on 26 May 2008 17:00:44

[Petrolhead]

 

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_{My site}

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[alextangent]

Have you checked all the rear suspension components are secure?

 

Alex McDonald

PASSED THE MOT!!!

[Beelzebub]

 

If the diff's been rebuilt has the bearing preload been & backlash between the CWP been set correctly ?

 

Sorry can't think of much else this late at night IYSWIM.......hic

 

D.

[Petrolhead]

Could the diff, an ex racing one, be set up too tight

 

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[ben7]

Thanks for the bump Pete.

 

As a sanity check, if you have one of these fitted and jack the rear end up, should the rear wheels rotate in the same direction or should they rotate in the opposite directions

 

Ben

[grasshopper]

Both wheels will rotate in the same direction, make sure your MOT tester know this as when they do a brake test they will rotate one wheel at a time and this I'm told could damage it.

 

I have a AP Suretrack as well and yes it's noisy and clonks too, but certainly doesn't do what you're describing. I did resolve one clonk by making sure that all the suspension bolts were tight - one wasn't

 

S7UPL - SUPerLight no.108

[ben7]

Thanks for the help Chris.

 

I ask as I spoke a very helpful guy at AP, who mentioned that the wheels should rotate in opposite directions, which got me a little worried!

 

Mind he was on a rally in Greece when I spoke to him 😶‍🌫️ and they haven't made the units for around 10 years apparently

 

Anyhow, I'll give them a call next week when they're back.

 

Out of interest Chris, how much play do you have on your wheels. If you look at mine and think of a clock, they move from 12 to 1 o'clock before they 'engage'.

 

Cheers,

 

Ben

 

 

[Shaun_E]

With the AP Suretrac the wheels rotate in opposite directions just like an open diff. They are an unusual LSD and don't seem to follow the same rules as the plate types. MOT brake rollers don't seem to cause any problem.

 

Yellow SL #32 - member of Drowned Rat Racing

[grasshopper]

Shaun, hopefully I'm not mistaken and mine is an AP Suretrack. I used Angus' reference material halfway down the page here to work out what diff I had (I had to change a broken half shaft, I didn't just take it to bits for fun )

 

In anycase, with mine both wheels rotate and I've decided not to risk single wheel brake testing for MOTs. I can't recall how much play I have before the wheels both rotate but it's not too much.

 

Alex may well have a point as well, I had a clunk that felt like a kick in the back and it turned out to be loose bolt on the trailing arm fixing under the rear wing.

 

Probably best to double check with AP when they are next available.

 

 

 

S7UPL - SUPerLight no.108

[ben7]

Well mine definately rotate the same way as well.

 

Somebody reminded me it's the WRC in Greece this weekend, perhaps AP were a little busy then 😳

 

I'll check me bolts and see if that sorts it.

 

Thanks for all the help,

 

Ben

[Graham Perry]

Ben, the symptoms you describe sound very much like you have a Universal joint on your driveshafts that is about to fail. Drving a car round in circles first one way and then the other to isolate which side was one of the first tricks my father taught me when he was trying to get me interested in becoming a garage mechanic. The series of successive small jolts being the significant bit to look for.

 

I am not saying it is that, but I would certainly check them carefully

 

Edited by - Graham Perry on 29 May 2008 11:11:07

[ben7]

Graham, that certainly sounds like what it sounds like.

 

I'll have a good look at it over the weekend.

 

Thanks for the help,

 

Ben

[SLR No.77]

With my AP Suretrac, if in gear the wheels rotate opposite ways, out of gear the wheel rotate the same way. Engine not running of course!

 

Stu.

 

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Joint Area Representative MAD Sevens (Merseyside And District)

www.superse7ens.co.uk..........the rebuild 😬

 

 

[Petrolhead]

This is interesting read ben from Angus's site - here

 

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[Graham Perry]

Angus's diff identifier is a nice resource

 

All it needs is the Sierra 4x4 viscous diff to be added (which isn't easy adaptable to a Caterham) and then anyone who is looking to buy a secondhand diff will know what to look for (or not) as his page would have every main variant of that diff covered.

[ben7]

Thanks for the link Pete (and Angus of course for taking the time to put it on his site!).

 

I'm speaking to AP next week. Aparently they have paper copies (design pre digital which makes even more clever!) of the original drawings that they're going to fax through to me.

 

I haven't had chance to investigate further yet ...