quaiffe or cusco centre diff ?????

Help,im looking for advice on which centre diff to buy,if it was down to price id get the quaife,but i would like to hear from anybody who is running these centre diffs,i have given up trying to locate a ralliart one,so am left with a choice of two,quaife or cusco ? /ubbthreads/images/graemlins/dunno.gif any advice would be appreciated,im allready running front and rear lsds,just need to sort out the centre diff.

 

[cheekychimp]

I think a lot depends on your intended usage and the sort of power you are going to produce. I have no wish to give Quaife bad press but it is well known that the centre differential they produce for the DSM/VR4 is prone to breakage especially in high horsepower and applications involving hard launching of the car.

Quote:
Hello everyone -

This is Jon Ripple of T.R.E.

I rarely make posts here but I'd like to clarify some things.

Last winter we noticed that people were breaking their Quaife center diffs.
We found that the backlash between the center diff and intermediate shaft is
a little excessive. This will cause gear tooth breakage if and when the
gears are heavily loaded. I've contacted Quaife USA and UK and explained to
them why their diff is breaking. The backlash issue is the major problem
followed by the heat treating. I discussed this problem with Mike W @ RRE
and he talked Quaife USA into sending some DSM parts back to Quaife UK so
they could see if anything wasn't to spec. After a while Quaife stated that
yes there is some backlash but they have to leave it because they do not
final grind the tooth profile after heat treating, leaving any distortion
from the heat treating process. To allow for this distortion Quaife has
elected to ride close to the acceptable limits for backlash. This will cause
variances and the end result is some gear noise. Some of you may notice
that after you've installed a Quaife you will here some gear whine,
especially in 3rd gear - no load. This is the backlash issue.

What is my conclusion? If you launch your Mitsubishi AWD hard enough the
Quaife center diff will eventually loose some teeth. Sorry guys but the
teeth on your stock center diff are stronger. I've been in a lot of DSM
gearboxes and rarely do I see busted teeth on the factory center diff gear.
Pruven Performance has cut several mean 1.32sec 60' times with the
transmission that I built for them without any breakage. That is a full
season without any breakage. That trans has the factory center diff with
the spool that we sell.

The size of the planetary gearset inside the Quaife center diff is a little
small for the power that a built 4G6x can belt out. The thrust/friction
surface of the sun takes a fierce beating. Quaife could remedy this by
reducing the combined thrust/friction surface area of the planets, allowing
them to wear evenly with the sun's thrust/friction area. This will also
provide the Quaife with improved Auto-Torque-Biasing.

I do not feel that I'm dogging Quaife. Overall they built the best limited
slip differentials. I like the ATB (Auto-Torque-Biasing) action of the
Quaife because it will send equal power to the front and rear diff when you
launch hard. However I prefer the 4 spider center diff from Speed Design
that we sell. It is well built and holds up the best for the money. If
the car only spends time at the strip then the Spool will work the best in
this application. More info on transmission upgrades can be found here,
click

Secondly- We have not used the EVO forks with the plastic wear pads ever
since Scott Hidley wore his out. Last spring we started replacing the
plastic wear pads with a Bronze alloy. To deal with the high load of fast
shifting, the pads have twice the surface area of the plastic pads. I have
put about 5k miles of beat-ass on a set of forks and they looked perfect
with hardly any wear. I would like to point out that most of the wear pad
issue revolves around improper clutch adjustment and trying to stuff it into
gear.



As a result, I'd be inclined to go with either a clutch pack or the 4 spider Speed Design differential mentioned. The Quaife unit is nice however and if you aren't launching the car or running a high horsepower engine you might be okay. I personally wouldn't take the risk but that's just me.

Paul.

 

Thanks interesting read, im running a tarmac rallycar with an 5 speed albins dogbox modified 4 spider with front and rear lsds with approx 300bhp and a quarter master twin plate,im not into heavy launching but you have to remember running on sticky rubber and 356mm discs and 6 pots,so im wrekin the centre diff as it is the weakest link,ideally i was looking for a ralliart viscous but have given up,so hence looking at alternatives,i will in the meantime speak to quaife uk to see what they think,it may be the only choice ? keep the advice coming as im open to options.

 

Ok, have spoken to Quaife uk,to be fair the saleman i spoke to was very helpfull and was not aware of any problems however he did reassure me as the centre diff comes with a LIFE TIME GAURANTEE which i thought was pretty good,and it is a stock item,im still open to suggestions or advice,has anybody got experience ?

 

[JSchleim18]

What happens if the Center Diff blows and ruins your transmission? Will they cover that?

 

[cheekychimp]

And do please double check that. I appreciate that it can't come with much more authority than from Quaife themselves, but the issue with exploding differentials whether it was the centre or front from Quaife was so common that at one point they withdrew that guarantee for 4G63 models. I looked for that information for you because I know I read it but I cannot find it. Either they bowed to pressure to reinstate the warranty, or they addressed the issue and re-engineered the part.

EDIT: Found it!!!

Quote:
Effective June 15, 2001, Quaife America will no longer replace broken differential housings on 76.309.155 (9B1) Center Differentials at no charge.

We have found that, due to design constraints of the transmission, the original equipment third gear that meshes with the center diff housing is prone to failure under extreme loading in modified vehicles. When this gear fails, it may cause the gear teeth ground on the Quaife housing to break, necessitating replacement. The Quaife Center Differential made for the Mitsubishi Eclipse/Talon AWD Turbo models are built from very high strength, case hardened material. However, even the superior construction of the Quaife Differential may fail under these situations, under no fault of the Quaife product.

Since this type of failure is not a fault of the Quaife product, we will not replace a broken housing that is due to this type of occurrence free of charge under the Quaife lifetime warranty policy. We will, however, replace the housings at a specially arranged price that covers our manufacturing costs.

All other components of this differential remain fully covered under our limited lifetime warranty.

For more info, contact our tech department at (949) 240-4000.



Link from RRE's website!

You might want to go back to Quaife UK and question them on that issue /ubbthreads/images/graemlins/dunno.gif

Is there any reason you are not happy with the idea of a clutchpack centre diff? I am not saying they are better, it was my choice but I reiterate I am not saying it is better, just wondered why you only seem to favour the Quaife?

Cusco does a clutch pack centre MZ model but they also offer a tarmac specific planetary diff with a 35/65 split/bias that is supposed to be quite good. One thing that has always worried me about both the Quaife and Cusco Tarmac diffs however is that when they lose traction at one end, do they not act like an open diff and send all power to the spinning wheels? I guess with both front AND rear LSDs as well the likelihood of losing all traction at either end is far smaller but I have always thought that in a hairpin, if you did lose the back end you'd be f*^#ed! I think the clutchpacks offer a little less finesse than the Quaifes and planetary tarmac diffs but I like the idea of all my power getting divided equally between wheels regardless of the road surface.

 

JS, ill bet they wouldnot pay a dime and theres probably a motorsport catch in the warranty "oh you used it for a rally,sorry matey thats not covered under warranty" i could tell you hundereds of motorsport warranty stories but thats for annother thread.

Cheeky,ill double check with Quaife may be get something in writing,i only started to go this route because they are only 1 hour drive from me and easy to call up,so ill put them on the back burner and am happy to look at the cusco option,ill see if they have got a distributor overhear,anybody got hands on experience of running the cusco ?

 

[Whoodoo]

Paul, I think you may have a slight misconception of how a planetary LSD behaves. It is my understanding that they have a maximum torque biasing ratio (lets use 60% for example. If the rear tires break loose on a tight hairpin, then up to 60% of the torque still being put down in the rear will be transmitted to the front. In order to get zero power transmission (if you have a rear lsd in the back as well), then both rear tires would have to be in the air.

The formula SAE car here at school has a Torsen rear diff (works similarly to the quaife differential) and because only the rear tires are driven, it works out quite well. Often times when driving, I'd get the inside rear tire spinning but still get good acceleration because torque was being sent to the outside tire. In that application it worked well because I don't think I've ever seen one tire off the ground. In a GVR4 however, it is quite possible to lift a tire, so I would say having a clutch type LSD in the back is best. As long as you have that though, a planetary LSD in the middle will keep torque to whatever axle set has the most grip.

As always, Im not an expert, so correct me if I'm wrong.

 

[cheekychimp]

Alan,

I understand what you are saying, but the guy that was using the Cusco tarmac diff said that as long as you had grip at the rear it was great because the car rotated better through corners and understeer was almost completely eliminated. But he said he wished he could have a worn viscous coupler in there still that would allow the 35/65 to operate but catch the rear if he lost traction. He stated that if the rear tyres began to spin together on sand, gravel or in the wet he got zero traction at the front and lost it completely /ubbthreads/images/graemlins/dunno.gif

Can a mechanical diff really differentiate between a tyre spinning in mid air and one spinning on a slippery surface?

 

[Whoodoo]

Yes, a mechanical LSD doesn't care how the wheel is slipping because it does not bias torque like the quaife. Planetary diffs are difference-in-torque dependent while a mechanical clutch type differential is difference-in-wheel-speed dependent.

 

[cheekychimp]

Yes but my question is if the rear wheels are 'really' spinning, what difference does it make if they are off the ground or not and why in that situation would the Quaife not direct all power to the rear wheels?

 

[Whoodoo]

If they are spinning on the ground, they are still putting torque to the ground because there is still friction acting against the tire.

Lets take the following example: quaife center diff, mechanical lsd both front and rear.

Lets say you have both front wheels on dry tarmac and both rear wheels on ice. If you give her some gas, the rear wheels have extremely low traction and spin. What is going to happen? you will move forward. Why? here's how it works: Because the rear wheels still have some traction, a percentage of that is being transmitted to the front wheels, allowing you to move. If you were to measure the torque at the front and compare it to the torque at the back, you would see a bias towards the front. If, like above, your diff has a 60% maximum torque biasing ratio, then there will be 60% more torque up front than in than in the rear.

Ok, new example. You have your front wheels on dry tarmac and the rear of the car is off the ground. Give her some gas, and you aren't going to go anywhere. Why? because there is zero torque in the rear, the diff cannot bias any torque forward (60% more than zero is still zero).

New example. Now there is a mechanical lsd in the middle. As soon as the rear wheels in either case (rear on ice or rear in the air) start to spin faster than the front, the clutches will do their work and send power to the front.

 

[H05TYL]

I was under the impression the cusco tarmac centre diff was intended to be used with the stock vcu,
this way you'll never get zero forward motion even if the rear wheels are off the ground.
note it still has the extended output shafts and circlip groove...

also found this on evolutionm - explains my understanding of things quite well.

Quote:
Now, what you're suggesting is to leave the VCU out, but just as has been mentioned, that would make for just an open centre differential. I don't think that's a good thing.

The one person I have talked to who has a Tarmac gear left the VCU on and says that since the VCU takes a finite amount of time to lock up, the Tarmac gear has plenty of time to exercise its rear biased characteristics. Perhaps more importantly, the VCU does not redistribute torque per-se. All it does is link the two output shafts together so that in the event one end slips, the other is dragged along with it. Actually, I should mention that the w5m33's VCU resides in the rear output shaft and the differential body, but it does the same thing in that the short of it is that its action is slip dependent. It is worth remembering too that the Viscous Coupling doesn't really solidly lock up until a remarkable amount speed differential is detected. In fact, it still only transfers a limited amount of torque. I've heard that the w5m33 stock center viscous is rated at 16kgf per 100rpm? Not sure, but it's something along those lines.



The Cusco has assymetrical torque split due to the leverages of its internal gearing.
-the VCU does not redistribute torque until a speed differential is detected, leaving torque distribution alone until one end is spinning more than the other.
-and even when spin is detected, the VCU takes a while to react and only gives a limited amount of torque transfer. In short, it keeps you from getting too crossed up.

 

[cheekychimp]

That sounds about right, but in practice what the guy was saying was that a good VCU did impede the differential in exercising it's rear biased characteristics (to the extent he wanted it to) but that a worn or sloppy VCU allowed it to function as (he thought) it should. He stated that the problem was that it was almost impossible to calibrate the VCU to ascertain how much wear was required to get the perfect results and that even if that sweet spot was hit, it was questionable how long that would last before the VCU became too worn and failed to provide the safety cushion it was designed to.

 

[Whoodoo]

i don't know if you can crack open the VCU, but if you could, taking out a couple of discs would reduce the amount 'grab' it has.

 

Is the Cusco Tarmac the only one that has the 35/65 split? The front end push is actually the only part I dislike about my Galant.

 

[cheekychimp]

I believe it is the only differential that offers the split but I 'heard' that some aftermarket VCUs offer a slower 'lockup' effectively counteracting the understeer (push) by allowing the car to rotate more.

 

[number3]

I had both the front and center installed in number3 and loved the way the car handled. (Quaife)

 

[cheekychimp]

To be perfectly honest Harry, your comments seem to be indicative of everyone using Quaife units. It could well be that the advantages of using these units far outweigh the potential disadvantages for 90% of us. I've always wanted to drive a car with Quaife diffs to see how they differ from others.

I read a thread a long time ago discussing the ideal combinations of diffs for an AWD circuit car and they recommended Quaife at the front and clutchpack or open at the rear depending on the choice for the centre which was either a spool/welded diff or a Quaife unit again.

Having read the above I am really wondering how a Quaife front, Cusco tarmac centre with Ralliart VCU and a clutchpack rear would handle?

 

I think I may start looking for the cusco tarmac. Anyone know what part number for a 91 US GVR4?

Thanks,