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View Full Version : Which diff ? Kaaz 2 way or Harrop truetrack



adamRSLC
21-05-12, 04:53 PM
Im tiring of the mini spooled diff in my circuit car , diff is a BW78 ( VL Turbo diff ) and have these two options available .

Car is solely used for track days so quietness isn't an concern , the Kaaz diff a friend has used for a while and are available as a 2 way only to suit my car and has been faithful for many years finally needing some maintenance after the last event . I've heard good things from the Harrop truetrack and keen to hear some more positives from people who use them on circuit events .

Requirements are it can take a beating , fit in my housing and I would prefer it to act like an open diff when turning into a corner under brakes .

Adam

lysdexia
21-05-12, 04:56 PM
for what you use the car for you can't go wrong with the kaaz

the harrop would be my pick for a street car, but for track work i'd much rather something with proper clutches in it. also if you pick a wheel up at any stage with the harrop, you'll lose drive to the one that's still on the ground, that could prove interesting if it happened under power

Walt Kowalski
21-05-12, 05:12 PM
I love my Kaaz. 1.5 way for circuit.

I think you use 2 way for drifting. Not sure.

Mine converts from 1.5 to 2 way by turning a screw inside.

Not sure about VL tho from what you said.

Babalouie
21-05-12, 05:26 PM
KAAZ 2 way won't be open on turn-in tho and most KAAZ 2-ways I've driven have lots of preload, so in fact are the opposite of open on turn in :)

TRD-RT81
21-05-12, 05:34 PM
trutrack for sure, you can probably get harrop to supply it with a pre-load pack if your worried so you never get the one wheel with y grip times one wheel in mid air (zero) grip situation but if you have an ecu with traction control it's a non issue. my Soarer has a T2 Torsen and the cressida has a trutrack (no preload pack) both have no issues street or track

Momus
21-05-12, 07:02 PM
Go the KAAZ LSD (or a full spool and save quite a bit of weight). Truetrack and other torque biasing diffs are good for the road and light track work and getting off greasy nature strips. No one serious races with them; they usually get removed and replaced with a Salisbury (KAAZ) plate and cam type.

You can change the overun wedge angle on KAAZ ramp cams to make an open diff while still having it lock hard on drive.

crack
21-05-12, 07:44 PM
2nd hand info / no personal experience: if you've got a corner (or a car setup) that wants to unload the rear inside wheel then you may have trouble with a torsen acting like an open diff.

adamRSLC
21-05-12, 07:49 PM
Interesting regarding the truetrack didn't realise it would open up if one wheel got some air , momus I have heard you can modify the 2 way so it's open on turn in and cornering but was unsure whi could do it . I've driven a similar Commo to mine with the Kaaz centre and liked the corner exit drive it got , I'm leaning towards this option and will try get it fitted in the next few weeks .

I know the full spool saves a chunk of rotating weight and allows more oil in the diff to boot , but I can't drive the car like I want too with the rear axle locked .
Adam

adamRSLC
21-05-12, 07:59 PM
Just skipping through eBay and $1350 seems the going rate unless any PF hookups can help ?

Adam

crack
21-05-12, 08:19 PM
The table in the ebay ad lists 2 way KAAZ for VN-VS 6 & 8 cyl as part no. DAG3820.

Only DAG3810 & DAG3830 are listed in item descriptions. You wouldn't expect price or availability to be any different but it is worth asking the seller about (that's if you want a 2 way).

260DET
21-05-12, 08:43 PM
Go the KAAZ LSD (or a full spool and save quite a bit of weight). Truetrack and other torque biasing diffs are good for the road and light track work and getting off greasy nature strips. No one serious races with them; they usually get removed and replaced with a Salisbury (KAAZ) plate and cam type.............................................. ......

Why is that? I've heard that so many times but have yet to hear a good reason for it. Other than one rear wheel off the ground, which should not happen anyway.

perthdrivers.jpg
21-05-12, 10:59 PM
1) wear in a clutch diff is easily fixable, wear in a Torsen is not
2) If a clutch pack fails mid race you can usually carry on, if a Torsen fails its catastrophic and you're out

From a performance perspective I don't think theres any realistic drawbacks to a good Torsen-type diff other than it being open under braking/decel which may not be desirable

Babalouie
21-05-12, 11:14 PM
Why is that? I've heard that so many times but have yet to hear a good reason for it. Other than one rear wheel off the ground, which should not happen anyway.

I think it's something to do with power level and likelihood of wheelspin. I've driven non-turbo MX5s with torsens and they're perfect, but for some reason, turbo MX5s with torsens can default to single legging sometimes. And MX5s don't lift wheels, so I'd say it's a wheelspin thing?

myliberty
21-05-12, 11:18 PM
I'd put a kaaz or cusco 2way in an mxv if I had one.

TRD-RT81
21-05-12, 11:54 PM
1) wear in a clutch diff is easily fixable, wear in a Torsen is not
Torsens don't wear like a clutch pack diff, they go many many times longer then a clutch LSD - clutch LSD's last if you shim them up hard like a locker if you set them to slip they are fucked in short order

2) If a clutch pack fails mid race you can usually carry on, if a Torsen fails its catastrophic and you're out
only Torsens i have seen fail is T1 Toyota Torsens that are drag raced or used for burnouts, T2 Torsens and trutrack's are MUCH stronger (much less moving parts and no small gears) and can be abused day in and day out without issues


From a performance perspective I don't think theres any realistic drawbacks to a good Torsen-type diff other than it being open under braking/decel which may not be desirable

260DET
21-05-12, 11:59 PM
The reason why I asked the question is because the Zed with 420whp through its torsen type performs perfectly on a circuit although it does not have a rear ARB.

200MPH
22-05-12, 01:00 AM
I've had clutch pack style (82 RX-7 turbo) and now have Torsen (Quaife ATB in GT40) for my track cars. RX-7 had race type ramps and it never wheelspun - until the cast hat cracked! It did push the car a bit (understeer) when under some power driving through mid corner waiting for exit. You could feel it essentially locking under power, but was basically open on turn in off throttle. Current Quaife ATB does not wheelspin inside wheel at all either, but it is in a car with rear biased weight (57% rear). Can see why you'd be setting up a high torque race car (V8 commode) with a rear end that was so stiff it would lift an inside wheel in any case - you want a softer rear essentially to get drive out of corners. A decent Torsen diff should not die or wear out either. My Quaife has an unconditional warranty, road or race track use. So I'm not worried by it busting, unlike my well founded worries about the rest of the transaxle...
Personal preference I guess. Both options should work well, but unless you yourself did a back to back comparison in the same car, you'll never know, and even then it may come down to personal preference as much as lap time. So spend up and tell us your thoughts after the comparison!

adamRSLC
22-05-12, 02:54 PM
Thanks for the information guys , I'm going to also give Harrop a call about the true track and just go over the benefits . They are the only place to source that centre as they modify an eaton centre from another housing to suit the BW 78 .

200mph , I'm at PI in June so will have some results by then
Cheers Adam

260DET
22-05-12, 03:20 PM
Agree that a soft rear end is what is needed to get power down with a grunty engine and a torsen type.

perthdrivers.jpg
23-05-12, 11:51 AM
Torsens don't wear like a clutch pack diff, they go many many times longer then a clutch LSD - clutch LSD's last if you shim them up hard like a locker if you set them to slip they are fucked in short order
only Torsens i have seen fail is T1 Toyota Torsens that are drag raced or used for burnouts, T2 Torsens and trutrack's are MUCH stronger (much less moving parts and no small gears) and can be abused day in and day out without issues

Yeah for sure they basically "dont wear" in a production, street-driven vehicle, but im talking about in competition where the stresses and loads on it will be sustained and far greater - that must accelerate the process surely.

And i agree that (as far as Toyota is concerned) only the 1st-gen Torsens had a reputation for failing, but im still thinking *potential* failure under sustained high loads (and the difference in failure modes between the two diff types, one catastrophic, one not) must be a factor in just about all motorsport using clutch-type LSD instead

Also just thought of another reason - Torsen lockup and decel/accel behaviour is fixed and cannot be adjusted whereas clutch packs can

Dont get me wrong ive had T2s in both my track and daily cars and never had any issue with them but just thinking why they are not more widely used in motorsport

data_mine
23-05-12, 02:41 PM
Never had a Kaaz, but do run a TruTrac. Do plenty of circuit/hill climb and the occasional drag. Never had problems with lack of drive (though I'm probably not lifting any wheels), But as said, pre-load can be configured so it won't happen.

And it's tough as too. The TruTrac has lasted several sets of gears, provides predictable handling at all times. I'd gladly get one again.

TRD-RT81
23-05-12, 03:35 PM
Yeah for sure they basically "dont wear" in a production, street-driven vehicle, but im talking about in competition where the stresses and loads on it will be sustained and far greater - that must accelerate the process surely.

And i agree that (as far as Toyota is concerned) only the 1st-gen Torsens had a reputation for failing, but im still thinking *potential* failure under sustained high loads (and the difference in failure modes between the two diff types, one catastrophic, one not) must be a factor in just about all motorsport using clutch-type LSD instead

Also just thought of another reason - Torsen lockup and decel/accel behaviour is fixed and cannot be adjusted whereas clutch packs can

Dont get me wrong ive had T2s in both my track and daily cars and never had any issue with them but just thinking why they are not more widely used in motorsport

stop start of daily driving is likely to be much harder then track work on a diff

Slides
23-05-12, 08:58 PM
The internals of a torsen are lubricated gear steel, not wearing clutch material, if spider gears or reduction hubs with similar gear interfaces/metal on metal friction last in a truck/Load haul dump machines that actually run heavily loaded for much longer time periods and duties than race cars, I think for the privateer that wants a car that turns in well, is predictable & drives out hard without having to rebuild a clutch type every weekend, they are the best choice.

You can change the torque bias dependant on drive direction (ie on or off throttle).

The vast majority of professional race outfit non-actuated (ie passive, no hydraulics etc) clutch type diffs are not set up like KAAZ etc, they are set with relatively low preload to avoid push/tyre wear with shallower ramp angles to provide more lock-up as drive torque is increased. They want them to slip/wear as this provides the best handling/turn in/use of grip circle for lap times. Having a "2-way" which is more like a spool until it starts to wear out means you have all the spool compromises with more cost.

Unless you are going to spec everything yourself in a clutch type and rebuild regularly I'd go the torsen, it will give the fastest & most consistent lap times unless the chassis needs to lift rears to give the front end grip.

trent from punchy
27-05-12, 07:10 PM
I put a KAAZ 1.5way in my MXV and its fine, no difference to under/over steer, a lot better at putting power down.

Momus
28-05-12, 04:23 AM
@TRD-RT81 23-05-12


Haha. WTF?

260DET
28-05-12, 09:41 AM
@TRD-RT81 23-05-12


Haha. WTF?

Answer my question, cunt :)

Ned Loh
28-05-12, 01:13 PM
I'd be worried about lifting a wheel.

In a competition only car, has anyone actually worn out a KAAZ 2 way in a BW in short time?

Having driven Kaaz in a BW I didn't notice it pushing, but that was on dirt. It was a little like a locker when getting it on/off the trailer etc, but who cares. & yes they make noise, but again who cares.

Momus
28-05-12, 07:39 PM
Why is that? I've heard that so many times but have yet to hear a good reason for it. Other than one rear wheel off the ground, which should not happen anyway.

Ok. Firstly, pro drivers do have a habit of getting drive wheels airborne..

Proper Torsens, and other, various torque biasing diffs are theoretically tunable for amount of torque bias (up to a finite limit) by altering the helix angle and gear teeth forms. These also consume horsepower when torque biasing because they are a friction device.
Salisbury ramp cam, all steel limited slip diffs are much more tunable. The ramp angles can be played with to alter the characteristics on drive and overun, the plates can be stacked to change the friction area which can achieve slightly different aims and the preload can be simply altered. None of these things are easy to change on a TBD.

lysdexia
28-05-12, 07:47 PM
I'd be worried about lifting a wheel.

In a competition only car, has anyone actually worn out a KAAZ 2 way in a BW in short time?

Having driven Kaaz in a BW I didn't notice it pushing, but that was on dirt. It was a little like a locker when getting it on/off the trailer etc, but who cares. & yes they make noise, but again who cares.

I do know of one dude who killed a borg warner one in an R31, but from memory it was covered under warranty with no problems, it was a defective unit

in dsturbed's old R31 GTS we threw my minispool in it for a drift day (the car had a stock cone type LSD at the time) and it obviously made it a pig of a thing to drive. the cone type never went back in, it was replaced with a kaaz unit shortly after the minispool went in, the car was night and day in terms of handling between the spool and the 2 way, the 2 way drove great.