aftermarket lsd for 944!??

[bazza]

hi

i want to know does anyone know or use quaife atb lsd for your 944!? and how is the different compare to those stock plate type lsd for 944 turbo s!?

seem this is the good lsd option for those 944 don have lsd in their car !

http://www.quaife.co.uk/Porsche-944-including-turbo-86-onwards-ATB-differential

 

[sawood12]

This is definately on my shopping list!! Although it is not an LSD, it is a torque sensing diff, or a TorSen diff and is far superior to an LSD in my view. An LSD is just a standard open diff with a few brass knobs on - it still sends the most torque to the wheel with the least grip until the point at which it locks. The TorSen diff proportions the torque according to the wheel with the most grip. It reduces understeer as the outside wheel is pushing harder than the inside - the opposite is true with a conventional open diff or LSD. The Torsen diff doesn't lock so in the case where one wheel looses all grip then 100% of the torque will go to the wheel that still has grip.

I'm not 100% sure so will bow to others 1st hand knowledge, but I get the impression that the 944 LSD is not that good really in that it is a clutch type, where a viscous coupled LSD's are much better, and the plate friction wears quite quickly, so although it is supposed to be a 40% locking diff the majority of the ones around now that have not had a rebuild will be alot slacker than that.

I'm not sure how much it would cost to install one as it looks a pretty tricky job but I reckon it would vastly improve traction. The thing that made the Audi Quattro rally cars so good in the eighties was not just that they were 4wd but the centre diff was a TorSen diff - which is what sets Audi's Quattro system apart from a standard 4wd system with LSD's (apart from the so-called Quattro system in the transversly mounted engine'd Audi's which uses VW's Haldex 4wd system, which is different altogether).

 

[bazza]

yes ! this look like those one they use for d1gb for those japanese on nissan 200sx by kaaz http://www.kaazuk.com/products.php

 

[John Sims]

ORIGINAL: bazza

hi

i want to know does anyone know or use quaife atb lsd for your 944!? and how is the different compare to those stock plate type lsd for 944 turbo s!?

seem this is the good lsd option for those 944 don have lsd in their car !

http://www.quaife.co.uk/Porsche-944-including-turbo-86-onwards-ATB-differential

I think I will start a rule that says you can't post such things on the forum .......mainly on the grounds of after seeing them I want them.

 

[Diver944]

It seems very cheap at only £693 +vat

One would hope that installation is - drop gearbox, split gearbox, remove old lsd, install quaife, reinstall gearbox

I wonder how many man hours that would be?

 

[bazza]

should we organise a group buy and get discount!?

 

[chrisg]

Further to another post I made a few weeks ago, there was an article several months (18 ?) in Porsche & 911 world about a team racing a 968 CS. They're 'secret' was using a torque biasing diff from the states which they were allowed to change under the PCGB Championship rules. Surely if they've done the swap out and fitted it, it must be straightforward to do ?

C

 

[Neil Haughey]

Sounds like a Guard ATB. Looking at the pictures of the Quaiffe unit it seems one has to bolt the ring gear on to the outside of the ATB diff, I wonder if given the transmission design on our cars one could easilly enough seperate the diff casing from the back end which presumably houses the gear set. Perhaps it wouldn't be too difficult. Personally I would prefer a plate type LSD with some form of easy external adjustment i.e. up the locking ratio for oversteery tracks then slack it off for street driving (so you can still reverse into parking spaces etc.)

 

[sawood12]

I'm afraid not. There was a post on this recently. The cover that expses the diff can be removed easily but unfortunately the diff bolts onto the crown wheel from behind it, therefore you need to remove the crown wheel which means splitting the gearbox from the bell housing. This may very well be a bolt in/bolt out job but i'm not sure about any setting procedure during re-assembly - I can't find that level of detail in my workshop manual. I'd imagine you want the gearbox pinion gear to be set onto the crown wheel properly so it is properly aligned and that the teeth are properly engaged.

I guess this would have been a similar piece of kit that was fitted to the 968's that had the optional TorSen diff.

Paul - I think that this piece of kit is just what Lil needs to improve traction.[]

Funnily enough while we are on the subject of transmission it appears to me that Audi seem to have pinched a few ideas from Porsche. In this months Porsche Post there is an article talking about the various developments from the 80's that Porsche were considering that never came to light. One was "Porsche Dual Clutch Gearbox" or PDC which from the description sounds very very similar to Audi's DSG. Another was an all Aluminium body that was 50% lighter than its steel equivalent - Audi A8 mk1 was all aluminium. If only Porsche had pushed ahead with these developments.

 

[sawood12]

Link to the other thread I was referring to...

http://www.porscheclubgbforum.com/tm.asp?m=266296&mpage=1&key=quaiffe&#266296

 

[Hilux]

How long would it take (labour wise) to drop a gearbox and refit?

Add the cost of installing the diff plus the diff itself and its all less than £1200?



Not that I`ve got £1200 [][][][][]

BTW the wife found out that my recent `MOT` and shock absorber replacement [] was a bit more involved (and expensive) [8|][8|][8|][8|][8|] so I dont think there will be any more expenditure for a while [][]

 

[sawood12]

Dropping the gerbox and re-fitting is a quick and easy job, but I reckon replacing the diff is a bit trickier, although i'm sure if you know what you're doing and have the right tools it is probably fairy quick job.

 

[jet951]

Hi guys,
first post on this forum, been lurking for a while though. just some info on the install of a LSD into the 944/968 box. both the 944 and 968 boxes have to be removed from the car, on the 944 series gearbox the rear gear section will need to be removed first, which is a series of 13mm bolts. the side diff cover can now be removed and then the diff removed. the crown wheel can then be unbolted from the old diff and installed onto the new LSD. now there are two procedures that must be followed to install the new LSD into the gearbox. one is Diff preload and the other is pinion backlash. the pinion depth and pinion preload will not affected. there are porsche specific tools to do this job but they are not essential. once the preload and backlash is set the side plate can now be reinstalled and then the rear housing reinstalled. the whole job should take about a days labour, depending on how good your specialist is.

the Torsen LSD is a very good street LSD and we recommend this on all our street/ autocross/motokhana cars. the problem with the torsen is that on decel there is no locking what so ever, this is not a good thing for a track driven car, the fact there is no locking on back off will tend to really unsettle the car mid corner. for the track we use a custom 4 plate(standard porsche 40% is 2 plate) 80% LSD. this is the only way to go for a track car. i use one in my 951 which is street track. the 80% is both 80% on accel and decel, thus ensuring a smooth transission between power and backoff. the standard porsche torsen is set to about 40% locking. Our torsens are about 65% locking. it really comes down to the use of your car.
Sean Buchanan

 

[sawood12]

Sean, I guess an 80% locking diff wouldn't be very good for street? I remember being in my friends rally car that had a diff with a high locking ration and on tight low speed manouvering eg in car parks and petrol stations the back end would skip as the rear axel locked up during tight manouvers and it then bacame a matter of which wheel was going to loose grip first. I'd imagine the stress this causes on the transmittion can't be too good.

 

[jet951]

Hi Scott,
we were worried about that same issue before we fitted our first 80%, but to our surprise, the car is completly streetable. i would go as far as to say i wouldnt use anything else. there are 2 factors which can cause chattering at low speed, reverse parking etc, one is the high locking value but more importantly the initial lock. a lot of people try to modify the stock LSD and place thicker shims. people believe this will increase their locking value, but all they have done is increase the initial lock. the ramps inside the LSD are what set the %. not the tention on the clutch plates.(although if the clutch plates are worn the designed 40% locking value will not be reached). so if the LAS has been manifactured properly there should be minimal discomfort at low speed, if any. by the way those guards transmission LSDs are not made by Guards. they are made by a company in Australia that we use.
Sean

 

[sawood12]

Are you sure the Torsen diffs you are referring to are the same as these Quaiffe ones? Reading the technical schpeel it says the diff never locks as it constantly varies the torque across the axel according to the amount of grip each wheel has.

 

[Neil Haughey]

Well when they say grip they mean load, which means the outside wheel which to me means that an ATB will cause a car to naturally oversteer whereas a plate type LSD is likely to keep the rear more neutral hence more a feeling of gentle understeer.

 

[sawood12]

Yes but if the inside wheel is pushing harder than the ouside as with a conventional diff and LSD then it is fighting against the steering and is contributing to understeer - i'm sure we've all experienced that when you push hard mid corner you induce understeer. With the ATB the power is complimenting the steering. Granted if you floored the thottle mid corner then you might very well induce oversteer earlier but this is an extreme case and the same is true with a conventional diff and LSD. In reality you employ throttle control and feed the power in gently. But in reality what would happen in an oversteer situation with the ATB is that the moment the outside wheen looses traction there would be a shift of torque to the inside wheel that still has grip therefore unless you've lost it big style it is self correcting. This doesn't happen with a conventional LSD as all that would happen is that the diff would lock and prevent all the torque from being sent to the outside wheel that has lost grip so the inside wheel still recievs some of the torque and therefore you retain some control.

Also i'd argue that an LSD is more likely to cause oversteer because as soon as the diff locks you've effectively got a solid axel which means one of the wheels has lost traction and is spinning and this is far more likely to cause oversteer. Don't forget the ATB (or the Quaiffe one at least) doesn't lock at all which means the wheels are rotating at the correct speed for the radius you are driving and in the case where one wheel looses grip altogether all the torque goes to the wheel that has grip.

Also because with a conventional diff and LSD the inside wheel is pushing harder then you are more likely to loose traction earlier as it is the inside wheel that is unloaded mid corner and therefore has the lease grip. With an ATB the torque is biased towards the outside wheel which is loaded and has more grip. A solid rear axel makes the car very understeery and when an LSD locks that is effectively what you've got.

Without doing a back to back comparison it is difficult to imagine which diff would be best for you. There are clear advantages of the ATB but it also has disadvantages, but the conventional LSD is fundamentally flawed as it is sending more torque to the wheel with the least grip.

 

[jet951]

Hi Scott,
in theory the Quaife/Torsen type(and yes they torsen type LSDs we use are identical to quaife) should be better, and apply more power to the ground. in reality its slightly different. in our 951(which we race) we have had 4 different LSDs. first was the original open diff which is a waste of time at the track as you said the inside wheel will spin causing the car to be very slow on exiting the corner.

next was the Torsen. under power it worked very well, even though the maximum transfer was only 60%. you will never get 100% transfer of torque with the torsen, the spinning wheel will always spin. the negative effect was terrible on the track, coming through a sweaper at say 100km/h with half to 3/4 throttle then releasing the throttle slowly back to 1/4 throttle would cause the cars weight transfer to be too violent. the fact the car has gone from grip to no grip(because its acts as an open diff on backoff) caused the car to spin. and yes the torsen does cause oversteer with power just like a conventional LSD.

the next 2 LSD i tried were very similar to each other. first a 80%accel, 60%deccel and then a 80%accel, 80%deccel. the transition of these LSD whether it be on the track or on the street makes the car completly controllable when having to back off, or for that matter under power. these our our real world findings. that same sweeper we could run the car faster through because we didnt have to worry about weight transfer thus better car control.

the Torsen is a great autocross/motokhana LSD because it will turn in very sharp on back off. because the car gets very unsettled you cann accelerate up to a cone and in one movement backoff and turn in, this will cause the car to spin getting around a 180degree corner quite quick and although the car control is not quite there it should be quicker.
the car we tested these LSDs on has about 380rwhp
sean

 

[333pg333]

Just to add to this. I have driven Sean's car on the road and you wouldn't know that it had a race lsd in it. There is no chatter, or crazy understeer. It is absolutely fine. I am in fact waiting for one to arrive so Sean can complete my gearbox. Also to note we have both changed crown wheel and pinion to S2 for shorter gearing overall but much better for track. How often do you, or can you travel at stock top speed of 270kmh+ so bringing this down is no problem. Being in the right gear on the track is however a massive advantage and the increased accelleration is also brilliant.