Penguinracer

Hi All,
my car needs to be tolerable on the road, but it's not a daily driver & it will mainly be used on the track. My question is: Am I better to get the factory LSD serviced & retain it or am I better to replace it with a Quaife.

I've heard the argument that for kerb-hopping when you get a wheel off the ground the LSD still does it's job whereas the Quaife requires a certain amount of resistance at both wheels to do its job.

I've driven a 250 bhp Quaife-equipped Mini Cooper S & it transformed the car - but that was a front driver. The final 968s got ATB diffs so Porsche was open to the Torsen type diff which can split the torque to a greater extent than a traditional clutch type LSD.

Opinions & experiences are welcome.

PorscheDoc

Exactly. Or, go with a Guards unit. It is about the same cost as the quaife. We have pulled a few quaifes out on 944T track cars because it wasn't doing it's job in the corners. We sent the units out to Quaife, and they went through them and said they were working as they should. They were replaced with guards units, and haven't had any problems since.

Wormhole

My preference is Torsen over LSD.
Some pros and cons..

LSD = More stable under threshold braking. Clutch is a wear item and is rendered useless when not serviced. Racers need a higher locking rate then OE.
Torsen = better turn in, 100% lock, no wear items. Not as stable under braking, but if suspension/brakes are tuned correctly shouldn’t make a difference.

M758

I have an open diff and drive an NA so take this for what you will.


Perference. Guard 80/50 LSD. Why? Lock up under accel, but most importanly lock up under braking. This adds stability for braking and allows greater use of trail braking. This allow you do brake deeper into a corner and around the corner. This can vital and some track and just important at others.

The torsen acts like an open diff at turn in which is a disadvantage.

Spidey944

https://rennlist.com/forums/search.php?searchid=3600808

numerous posts, all pretty much saying the same things....

A.Wayne

Guards is the way to go .........................

TonyG

You need to be very clear here about your terminology.

Guard makes a torque bias differential, just like the quaife, and like the Torsen Gleson.

Furthermore, Guard makes a conventional clutch pack LSD in addition to their torque bias differential. You cannot compare the two.


Any torque biasing differential (ala quaife or guard torque biasing differential, torsen gleson) will be horrible on the track.

The last differential you ever want for a track car is a torque biasing differential because it acts like an "open" differential under braking. No difference.

You want a good deal of lockup under braking so that you can trail brake effectively without the rear end getting loose and coming around on you. With an open or torque biasing differential you can't. With a LSD that locks up you can. The difference is night-and-day.

The problem with conventional LSD's is that you have to shim them real tight to get them to lock up enough under deceleration to be effective. While this is good for trail braking, it's not good for cornering under acceleration as the car will tend to push.

This is the exact reason why the Guard GT LSD differentials are so great. They are asymmetrical. Meaning that they lock up at x rate under acceleration and y rate under deceleration. You get the best of both worlds.

My Guard GT LSD is a 50/80. This means that it locks up at a rate of 50% under acceleration and 80% under deceleration. And boy does it work.


Anyway, the choice is clear:

Street Use: TBD (torque biasing differential... Guard, Torsen Gleson, Quaife) - - - but I really see no reason not use use the proper clutch pack LSD on the street anyway. Almost all factory Porsches (back almost to forever) have used clutch pack LSD's with the exception of the '92 968 and maybe one or two other cars... but even Porsche abandoned the torque biasing diffs in favor of the clutch pack LSD's (in cars that came with LSD).

Serious Track Use: Guard GT LSD Asymmetrical ( in the case of the 944... a 50/80)


Track Use on a budget: Factory LSD (which needs to be rebuilt if it's got 75k+ miles)


TonyG

Penguinracer

Thank you all - you've been really helpful & informative.
Your advice has led me to decide that the Guards 50/80 LSD is the diff for me.
It's great to be able to call upon a community of petrol heads for advice & education. Thank you.

anders44

on the interesting side, quaife will only sell you a torque sensing diff, even if you buy a sequential transmissin for your 996, or GT40.

333pg333

I thought the ratio was 80/50% not the other way around?

TonyG

They are 50/80 (50% acceleration/80% deceleration).

And you can definitely feel which is which on the track at the limit of adhesion .


TonyG

TonyG

Here is a great article to read from Velocity magazine (the POC publication, for racers by racers...)

I highly suggest everyone here read this.

http://www.guardtransmission.com/velocity.htm


TonyG

TurboTommy

Needs to be rebuilt at 75k track miles, or total mileage on the car?
What kind of driving, or manuvers, promote the greatest wear?
What's involved with the rebuild? What all can one do "while you're in there"?

gt37vgt

i would have thought 80% on decel would be a shade to much for a front engine car .i would kind prefer it the other way around .
also there must be a piont at wich to much decel lock give the handbrake effect making the car unstable
also the car has to engine brake a bit to get the decal lock to work do other people with half the engine see the profond results tony sees with 8 cylinders locking up the diff during braking ?

I'm not convinced that torsin diff's are no good in a front engined car on the track but I'm not posting in the top 5 quickest like tony