Limited slip differential problems

Non-engine, eg: aerodynamics, gearboxes, brakes, suspension
cantfindausername
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Limited slip differential problems

Post by cantfindausername »

A little background info first off.

On Saturday I managed to drive my car for the first time in 2 years. There were some teething problems to start with but eventually got it going.

I have a Kaaz 2 way LSD in the transmission, and I'm running semi synthetic 75w90 gearbox oil in there, so no friction modifiers yet.

I know I need to run the LSD in, and when I'm starting off on full lock the car is really banging from the Diff. This I can understand and deal with in due cause and run it in properly when I'm legal to be on the road.

However, it has developed a sort of ticking/clicking noise when driving in a straight line. This sound I haven't yet been able to place.

So far I've only been able to take the car up and down the estate where is is kept. I don't want to keep driving in these confined spaces as it means having to make tight turns, but the car isn't legal to be on the road yet so I can't open it up too much. I would ideally like to get these niggles sorted before taking the car for an MOT.

So my question is really this: Has anyone experience such noises with new LSDs?

I have not yet checked for stones in the tyres, but think I will later tonight.

Thanks,
Ant
Last edited by cantfindausername on March 22nd, 2007, 4:28 pm, edited 1 time in total.
Guy Croft
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Post by Guy Croft »

Not propshaft joints?

GC
cantfindausername
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Post by cantfindausername »

Its a mid engined car so no propshafts, but the driveshafts did spring to my mind earlier this morning. I've have had new uprated inner CV cages put in so will do some investigating on this too.

Ant
Walezy
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Post by Walezy »

Does this klicking sound appear when you turn to one side and dissapear when you turn to the other side? I had this problem when I had to use spare wheel in my rally car and it was not exactly the same diameter. It was the diff working all the time and making that klicking sound(colotti LSD). maybe one of the tires is worn too much? If your diff has high locking ratio then this sound normally appears then turning(especially in parking lot -most people are thinking that your car is a wreck :) ).
Lowtechguy
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Post by Lowtechguy »

lack of CV grease on the driveshaft spiders, either cause from old or lacking lube when you fitted the lsd or a rip in the cv boot. Symptoms have happened to me 3 times in my life and was the same problem on 2 different cars.
cantfindausername
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Post by cantfindausername »

Thanks for the replies fellas,

The wheels and tyres are all brand new, so should be same diameter, unless there is a moulding problem.

I think it has a near on 100% lock at the moment as I'm not using friction modifiers, so the noise when manouvering is aweful and bangs violently in the cabin.

LSD is installed in the g/box itself so is lubed by the gearbox oil. All the CV boots are brand new also.

Good to hear some alternative examples of noise as I've been unable to get much information off the net so far regarding this!

As for the car sounding like a wreck... that is a dead cert! Especially with the twin plate clutch clattering away as well!

Ant
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Post by sumplug »

Noise is proberly due to the LSD being near or at 100%. Unwind it a bit and see if it stops.

Andy.
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Post by cantfindausername »

Can't unwind it. Will try putting friction modifiers in the oil as this is the only way to adjust it as far as I'm aware.
Walezy
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Post by Walezy »

I understand that it is klicking all the time, this is standard for such LSD but it should not happen when you drive straight as the diff should not work at that time. if this klicking sound appears when going straight then I would look closer to this as a big problem may appear.
cantfindausername
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Post by cantfindausername »

yes thats what I'm concerned about. It wasn't doing it straight away which also concerns me.

I'm very nervous about things going wrong, so don't really want to do too much without having checked out all possibilities I can.

Thanks for the input.

Ant
TR-Spider
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Post by TR-Spider »

That "banging" noise at manouvering, starting at full lock is so called slip-stick effect, i.e. the clutchplates in your LSD are not slipping, they are snapping from sticking-sliding-sticking. The snapping then bangs the teeth of the gear wheels. Usually this noise reduces when the oil gets warmer (and thinner, so it can easier fill the gaps between the clutchplates).

Do you know the number of clutchdisks and the geometric sizes? Then you can calculate the lock%, i.e. the percentage of transferred momentum to the unloaded wheel. 100% may be a bit much if you intend to drive around corners.

Thomas
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Post by cantfindausername »

I wasn't aware of that. I knew to expect the banging on corners. Didn't know you could work out the %age though. I thought there was an eliment of guess work to be honest. As for actual sizes, I can't find this information on their sites.

This is an exploded view of the LSD, can you count how many plates there are? Hope its ok to post? If not, please edit to just a link.

Image
sumplug
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Post by sumplug »

Most Kaaz LSD's are shipped out with 8 clutches on each side.
The diff is shipped in what KAAZ calls the 100-percent locking configuration, which, if you continue to call the differential plates D and the axle plates A, means each side has the plates stacked DADADADA. Every time there is a D next to an A, there is an active friction surface helping you do powerslides. If you swap a few plates around and stack them DADAADAD, you knock the number of active friction surfaces from 8 down to 6. KAAZ calls this configuration 75 percent locking. You shou;d never use 100% lock as this effectively makes the axle solid and will not allow the vehicle to turn. Use only 80w/90 GL-5 and not synthetic. Use the figure of eight to run the diff in.

Andy.
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Post by TR-Spider »

The locking rate isn't guesswork, really...more physics...

I made me a small calculator while beeing in the process of tayloring a new LSD into my Fiat 132 axle.
The only guess was the friction coefficient, now the calculator matches nicely with the locking rates given by ZF.

Just by calculating the Kaaz with the dimensions of my ZF, the 100/75% numbers with varying friction surfaces seem to make sense. For accurate calculations, you should put in the geometric data.



Thomas
Last edited by TR-Spider on August 20th, 2007, 4:55 pm, edited 1 time in total.
cantfindausername
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Post by cantfindausername »

Thanks guys, will have a look at that.

I am wondering if the clicking noise I heard was it slightly engaging as the road I was on was a gentle turn, no I possibly wasn't going 100% straight.

I don't think I'll be pulling the transmission just yet to make adjustments. I'll try first with LSD addatives & modifiers etc. THink i'll take it for a spin (not litterally) tonight and see if I can pin point it on a straight stretch of road.

Will report back with my findings!

Thanks for the calculator too. I will have a look at that in a while too and see if I can get some more figures.

Also, the 8 plates each side, I think is right. I read somewhere that they are 16plate LSDs.

Thanks,
Ant
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