LSD - symptoms like clutch slip?

[Paul Deslandes]

I don't really think its likely or possible but, before I rip the engine out to get at the twin plate clutch, can a faulty plate type (Titan) lsd exhibit symptoms similar to clutch slip? Its ok on launch but stepping on the gas, in any gear, the revs rise just as though the clutch is slipping and then grip again with a slight judder. I'm really surprised if its the clutch that's worn but it almost certainly is.

 

I'll call Titan tomorrow but interested in any views on here.

[Willie.]

Could the clutch be contanimated / faulty rather than worn? Problem with pressure plate or make crankshaft oil seal leaking and it's got onto friction plate?

[Jason Plato]

what diff oil are you using ? . I had similar and reverted back to Castrol

[revilla]

Surely even if the slip-limiting system within an LSD packed in completely and was allowing the diff to slip freely - you would still be left with what is in effect an open diff, which wouldn't allow the kind of slipping you are describing where the engine revs increase?

[Jason Plato]

thats right Rev, you would have thought so....

 

but it feels as if the torque is not being transfered to the other wheel and its as if the LSD if simply spinning and not transmitting any or limited drive.

 

 

 

 

[Paul Deslandes]

Thanks for replies.

 

If it was clutch I'd expect it to keep slipping, rather than slip and then grip whilst keeping loud pedal down. Its also a racing twin plate although I guess they can wear out too.

 

I can't remember what oil I put in the diff now but it included a friction modifier, and both were as recommended by Phil Stuart.

 

I've just spoken to Titan who confirm that it sounds like an LSD problem, probably a drop in pre-load. Its the slight judder/clonk, more felt than heard, as it locks up that makes me think its diff rather than clutch.

 

Road tax runs out at the end of the month so SORN, diff out and off to Road and Race methinks.

[Jason Plato]

Id try changing the diff oil first to Castrol LS

 

 

[Paul Deslandes]

I think that's a good idea Dave and will do that first. Am I right in thinking that the LS doesn't need a slip modifier additive?

[Jason Plato]

correct

[The Pikey]

My Titan preload was set at 40 lbs ft. It dropped to 20 within a short time. Never felt any slip at all.

 

 

[Birkin S3 ZA.]

Even if you take all the discs out it still wont slip when accelerating unless one wheel is spinning.

the discs let a certain amount of slip from one wheel to the other when cornering or when one wheel try's to spin faster than the other.

There is direct mechanical drive to both wheels through the prop shaft - diff - drive shafts - hubs.

No plates to slip unless one wheel spins faster than the other one.

When I fitted a paddle clutch to my ford turbo sierra it slipped for the first day every time I put foot.

It would slip for a few seconds and then judder and bite.

The paddles on the clutch plate must work a bit like race pads, they get better friction with a bit of heat in them.

Setting of from a standing start will cause some heat and no slip, when you accelerate with a cold clutch it will slip then bite.

 

 

Chris.

 

Edited by - Birkin S3 ZA. on 13 Sep 2013 08:00:11

[7 wonders of the world]

Assume you've tried driving in 4th holding the road speed by left foot braking and applying a good dose on the load pedal, if you get an increase in rpm without any increase in roadspeed you have clutch slip.

 

LSD wise - You can set a plate LSD set to zero preload and it will still work if the rest of the components clutch packs, ramps, sun and planet gears etc are all functioning.

 

If the plates were worn it would operate as an open diff and spin up the more lightly loaded wheel as the clutch pack will be unable to transmit the torque - as in a normal clutch.

 

On a 7 having a low preload is beneficial to aid initial turn in, most original CC supplied ZF's were set at stock preload for tintops in the range of 60-70 lbs/ft which is why they contributed to understeer an needed to be rebuilt accordingly to operate correctly in a lighter vehicle.

 

Higher initial preload leads to more wear as this preload has to be constantly overcome in order to achieve a difference in road wheel speed, therefore creates extra drag which affects turn in as previously mentioned, also generates more heat, and promotes the chirping/ judder most noticeable when reversing - though the friction modifier reduces this by effectively reducing the surface tension in the oil and helping it sheer in a more controlled manner.

 

[Rob Walker]

As Dave jackson posted we both had the same problem at Le Mans bugatti circuit on the left hand corners the cars felt like the clutch was slipping and the car lost drive. Stripped the diff at R&Race nothing wrong. Changed diff oil to Castrol LS and the problem went away. Note this was only in Left hand corners with the car on the limit. If you have slip in a straight line I would look somewhere else as one wheel is fixed drive with the Titan or ZF plate LSD's.

 

Rob

[Paul Deslandes]

thanks for that clarification Rob, my symptoms are in a straight line and, as far as I can tell, I don't have one wheel loosing grip so its beginning to sound more like clutch, which is what I originally thought before exploring the LSD idea. If the weather dries up in the next couple of days I'll try and do a more objective test before tackling one end of the car or the other.

[sjmmarsh]

Paul

 

Did you solve this? It sounds similar to what I experienced in my car today - 6th gear, 50mph, press the loud pedal hard - revs jump about 500rpm before the speedo moves to the equivalent speed and then it accelerates as normal.

 

I suspect it is the clutch, particularly after 6 years of sprints, trackdays and 35000 miles...

 

Steve

[Paul Deslandes]

Hi Steve. No I haven't got any further with it as the car is still sitting in the garage waiting for some attention . I'm pretty certain it's the clutch and hope to get the engine out in the next few weeks. Being a twin plate Superclutch, they apparently do manifest slippage with even relatively small amounts of wear.

Paul

[sjmmarsh]

Paul

Have you an update on your clutch problem?

Steve

[Paul Deslandes]

Hi Steve

it was the clutch and both driven plates were well past their wear tolerance according to Superclutch.  These were replaced and all is well again.  They're cerametallic plates and squeal when taking up, which is a bit unnerving at first.

Having said that, the old plates still have a lot of meat left on them and the need to replace is detirmined  entirely by the limited amount of movement allowed by the clutch cover mechanism. If I was getting through a set of plates every season or so I would seriously consider having the cover pillars machined and a set of spacers made so that the wear could be taken up by moving the cover progressively closer to the flywheel.  At £300 for a pair of plates the investment would be well worth it.

Paul

[sjmmarsh]

Thanks Paul

looks like I will need a new clutch soon then. 

steve