as always, hilarious and informative!

I will throw there hat into the running.

 

rjg,
If you're considering a limited slip, then have it done while replacing the ring gear. As far as where to go, I suggest Boulder Nissan as well, simply because they will probably have all the different shim sizes in stock for your diff swap, where an aftermarket shop might not. Something to ask of TC in any case.
As far as diffs go- like everything that's personal preference. The article Robert mentioned was in SCC and had good information on the charicteristics of each diff. If you are wondering between the Quaiffe and a clutch type, then here's what I can tell you. The Quaiffe by design will maintain a torque bias much higher than a clutch type can, often exceeding a 6:1 ratio. In other words, with both tyres on the ground to have some traction, the Quaiffe can still deliver up to six times the torque to the wheel with the most grip as the tyre with the least grip can accept before breaking free. That is it's number one benefit. The Quaiffe is seamless in it's operation, but has a high parasitic loss. It also generates more heat than a clutch type. Most people can understand the heat generated in a clutch, but the friction and torque bias across all those gears generates a tremendous amount of heat as well. The cons to the Quaiffe consist mostly of it's need to have both tyres on the ground. If one tyre is lifted, then the bias ratio becomes infinate and zero torque is transferred to the tyre with grip. Not good on ice or doglegging the rear at a track, such as coming onto the rumble strips too hard in a turn.
The clutch types are nice because they rely on simple friction to transfer torque. Most are pre-loaded with springs, such as the Cusco RS and Nismo, to place the clutch packs together. The clutch uses ramps that engage the pinion shaft. The ramps can either engage under acceleration, or both acceleration and deceleration. A 1.5 way diff simply has a lower ramp angle on the deceleration side so as not to engage the clutch pack as hard as it does on accel. This would be the way to go if you get a clutch type. The better units would be an OS Giken or ATS Carbon diff, but they are pricey. They use a better clutch type made of carbon fiber and carbon to keep temps way down and engagement consistent with use. They are virtually silent, and the degree of lock up the clutches provide can be altered upon a tear down and clutch disc reversal. The cons to clutch types center around a lack of bias ratio compared to the Quaiffe. Inherently, the clutches are working to keep both axles rotating at the same velocity, and therefore may break traction on the tyre with the least amount of traction before a Quaiffe would. Using a clutch pattern with less lock up would help, but also decrease the over all torque load they could handle from the pinion. So, it's a trade off, too low a lock up and the diff becomes useless and generates a lot of heat. Too much, and you have easy throttle oversteer.
The article in SCC pretty much summed this all up. The interesting thing is that the Quaiffe generally requires more steering input to correct than a clutch type, from the data in the article. But, it is a lot smoother engaging and as such allows more prodigous use of the available torque, so you'll be playing with the throttle a lot more as well. Smash the throttle too much in a clutch type while in mid-turn and you could have the throttle on oversteer. The Quaiffe stands a better chance of preventing that wheelspin as long as the tyres can handle the torque. The Quaiffe will certainly have more corner-entry understeer than an open diff car would, but any LSD car will suffer the same fate. The rear tyres pushing with the same torque will inherently try and keep the car straight, and any LSD will have a brief lag as the weight shifts and traction on each tyre is altered. The Quaiffe will come around sooner though than a clutch type (typically) since it has the higher bias ratio, and thereby allow more steering input before breaking traction.
For my own ride, I haven't decided. I love the Quaiffe and love the warrenty, feel, and general performance. But the new carbon clutch types from ATS and OS Giken are tempting with there lower temps and lower parasitic loss. And they could be reconfigured for different tracks with a teardown. Of course, who's going that hardcore? If not you, then the Quaiffe will be the best bet.
Will

 

Holy Informative post Will!!!

 

+infinity.

Seriously, thanks for the brain-dump. Excellent information man! Appreciate you taking the time on this matter! I'm now just stuck on the whole 'if you are doing 3.9 you might as well do a quaiffe...'.

BTW, does anyone know if there is a cheap way to raise your rev limiter without a utec or reflash?

 

I had a Quaife on my old Evo 8 and it howled like no other. It was so loud it was annoying to drive the car. Might want to some more research on it. I'm quite happy with my OEM LSD. I haven't done much research on aftermarket LSD for the Z but don't know why someone would want to change it. I change my Evo front LSD cause I broke it at Bandi.

 

for me it's the idea of more/better power delivery, esp. out of turns, plus a lifetime warranty (even for track/race use) which is hard to argue with. And then the whole cost of the 3.9 install, i'm just thinking if I might do a lsd swop later, I should really really try to do it now and save money...

 

That was me!! And I called TurboXS about it. Also called the seller of the code. Seller says they have heard of it very rarely but know someone else who has. TurboXS is looking into it. Will post more when I know more. Mainly how to make it stop!

 

ah, that's cool man, I couldn't remember your handle. Definitely keep us posted, appreciate the info.

BTW, Are you running test pipes? Sounded sweet if I'm thinking of the right pikes peak z.

 

Yep, Megan Racing. Not jet engine level like Kevin but a nice note none the less, best 9hp $100 dollar mod ive ever done. I was shocked to get 9hp out of it

 

Rick - I'm glad to hear that someone local is doing that 3.9 swap - it's something I've thought about doing for a while, so I'll be curious to hear your thoughts on it.

And while you're doing that swap and possibly a diff upgrade, you might consider spending another $80 on the Nismo heat sink/diff cover to help keep temps under control back there:

http://www.mynismo.com/products/?id=2788

 

I was considering ordering this w/ my stock diff. Think its a good investment now Gary?

 

Hey Gary, thanks man! I had read in a thread about that item but wasn't exactly sure where to find one. I will definitely do that as well.

Expect a full report sometime later this month (weather permitting). I'm glad I've got the Utec and the ability to raise my rev limiter, so I should be able to really take advantage of the new final drive.

Thx again,
rick

 

Cool, thx man, yeah, good deal on those test pipes. Sounded great without being too crazy. I need to pickup test pipes sometime soon...

 

Ive installed Quaifes in Hondas, Scions, Toyotas, Mitus, and hopefully 350s in the near future . I have never heard one wine unless it was broken. Are you sure it was installed correctly?

BTW we are a Quaife dealer if that helps. I can get you a decnet price on the unit if you decide to have it installed with the final drive at the same time. Juztin is correct, it will save you some labor time when all is said and done.

 

Thanks, I'm still deciding on the diff upgrade. PM or post your price if you don't mind, I am back and forth on this and I have 2 weeks until my wife returns from japan with the 3.9 gear.

Thx!

 

Can she some back with an Amuse exhaust for me. LOL

 

ha! took a bit of smooth talking to get her to lug back the 16 lb gear...

 

Hmmm... my buddy had a Quaiffe in his old 240SX and it was silent. The RX-7 came with a helical in it and it was pretty silent too. I had a Quaiffe in my B15 and it didn't make a sound.
rjg, just remember that for the most part, the Quaiffe will be silent compared to a clutch type and very stealth on the street. It will cover you for the broadest amount of driving in terms of getting power down to both wheels in proportional amounts. The clutch types I think stand a chance of being marginally better when they are perfectly dialed in for a particular track and torque level, but are willing to tear it down every time you go to a track and back? If not, then one setting will work but you'll put up with either more noise on the street or probably less performance on the track compared to the Quaiffe. After thinking about it over night, I would recommend the Quaife for you. I know you won't be sorry once it's in there and you're back at PMI. My .02 anyways,
Will

 

Thanks Will. I'm sold on it, I just don't know if the wife is sold on the idea...

 

Its easier to ask for forgiveness than to ask to buy it. LOL