Limited slip, worth it?
 

As a refresher, how does the limited slip work? Also for one who does not plan to race, would it be advantageous (especially cost wise) to change to a limited slip differential? Thanks.

Worth it? Of course it is. The difference from one wheel drive to 2 is pretty significant. As one rear wheel begins to slip, the other is engaged through a viscous coupling (sport package feature). If all you do is drive on the street, don't drive aggressively and don't have to deal with snow or seriously inclement weather than No, it may not be worth the cost to you to install an aftermarket unit ($1000+). Apparently you didn't see the value in the sport package, so the money (for you) would probably not be well spent..

Modshack
 

Thanks for the reply and it makes sense. Your assumption that I didn't see the value in the limited slip is mistaken. It would have meant buying the sport model and I couldn't afford the price difference at the time. Sometimes we have to make compromises and this was one...for now.

My 350Z didn't have LSD, and now I have it on my 370. You can't tell the difference in normal daily driving. I would say that the car feels a lot better on hard launches and cornering, but the 370 is a different animal than the 350. But with LSD you get power delivery to both wheels, which sounds a lot better than one.

For ElmZ
 

Thanks for a great reply. That really helps me as I am trying to decide what mods I will go to eventually. I have to deal with snow and ice (no choice for now) and I like to drive on really twisty turny roads which we have. In what ways would you say the 370 is a different animal from the 350? The reason I ask is, I like both and am thinking about buying a used 350 in a few years to modify but leave my 370 stock. Its just an idea and may not pan out. Again, thanks

A LSD is highly recommended for track use or spirited mountain driving. The OEM VLSD is decent for street use, but quicky overheats and turns to crap on the track. And because it is not a clutch style locking LSD, it can't put the power down as cleanly off the corner as something like a Carbonetic Carbon 1.5 LSD or OSG 1.5 way can do.

That said, I would look at upgrading to coilovers, and better brakes before moving to the LSD.

Sharif@Forged
 

Great advice. I am storing all this up for the future. I didn't ask about prices because I was afraid to, ha ha

Well I owned an 05 350 which means it was the 1st gen motor which we call the DE (03-05 DE, 06 Revup, and I believe 07-08 HR). With that said I had the slowest generation of the Z's with only 287HP. Now I own an 09 370Z + Sprt Pkg with 332HP. The 370 is a much better car than my old 350. It's got more grip, more power, and handles much better, so it makes it hard to compare. I can't tell for sure if I'm really feeling the LSD working or if its because the car has a lot more grip and more power. I'm sure it would be more noticeable on a track. I'll be doing AutoX this year so I'll let you know then :tup:

How does the LSD actually work? Does it deliver more torque to one of the rear tires (i.e. the one that's not "slipping" so as to compensate for the other one's "fail")? Thanks.

Torque sensing differentials can do that (Torsen for example). The Viscous unit uses perforated discs, rotating in fluid. The discs are stacked such that they alternate for the 2 output shafts, so when one axle is going faster than the other it will generate a hydraulic force against the other to speed up the slower axle. Unfortunately as the fluid heats up it loses it viscosity which makes the whole system ineffective.

ElmZ
 

Thanks, that is good information and gives me something to consider. I am reluctant to make too many mods to my 09 Z I guess.

Def worth it if you like to drive in the twisties. but like ChrisSlicks said, you could put a better unit than the stock sport one. Sinc eyou have to pay for the install anyway, I'd go that route and do it right.

Actually, I have the slowest of all 350Z's. An 06 that weighs about 150lbs more than the 03-05 but with the 5AT which means it came with the older DE engine at 287 HP instead of the 300 hp rev-up for the manual that year. I do have the LSD on mine and you simply cannot break the backend loose on that car. I can definately feel it working on hard slide cornering. From what I've read, they do tend to freeze up after 40 to 50 thousand miles but when they fail, the exactly mimic a normal non-LSD differential.

Good advice
 

Great advice. Sounds like the way to go is with a premium after market unit. Mine non-limimited slip model breaks loose very easily.

Thanks, ChrisSlicks! Is that the same as PosiTraction?

PosiTraction was a trademark name used by GM in the 60's for the LSD they were putting in their vehicles.

the lsd will heat up even on straight lines. mine did (along with another nismo) and for a good 30 minutes or so, won't go forward. admittedly, I didn't "break in" my car when I drove a sustained 140mph. how breaking in would affect the lsd unit? I don't know.

I just replaced the oil and it's been good so far.

The sport package is totally worth it. For ~$3000 more, you get syncro revmatch, 19'' wheels w/ tires, bigger brakes, VLSD, front lip, and a rear spoiler.

Aftermarket wheels and brakes will cost you that alone!

Just curious. Since viscosity is a major factor for the stock LSD. Would it be safe to say changing the fluids every so often will keep from failing? Like oil changes. Maybe go with a thicker fluid.
Also with the stock sport LSD, does aggressive gear shifts in straight line driving effect it? Or is it only cornering? Some Z's that are FI can wear out te stock LSD with aggressive off the line starts fast right? Thanks.

the fluid that fails in the stock lsd is the silicone fluid inside the sealed cartridge in the ring gear carrier (a little can in the very nuts-center of the diff) changing the 90w fluid will only keep the gears and bearings feeling happy.

Torsen, positraction, quaife are all the same helical type units with very minor differences, that use inter-meshing worm gears instead of the tradition cone shaped spider gears (the little ones inside the ring gear carrier) that due to torque differences between the two wheels are capable of sending a ratio of of torque from the wheel with the least traction to the wheel with the most traction provided that both wheels have some traction = if you lift a wheel or are in snow it acts like a one wheel wonder.

Clutch and viscous types work on rpm more than torque so if one wheel is spinning faster than the other, it starts locking. If its a really touchy clutch type it means it won't want to turn a corner at slow speed which makes parking lots a pain (properly set there are clutch types that don't do this that much). The reason a viscous doesn't do this is because instead of having friction plates it just has smooth steel plates spaced close together with a bunch of holes in them, and a thick silicone goo that when spun fast enough (one wheel starting slipping crazy) the molecules of silicone work like shoving a stick in between all the holes locking them together. Trouble is the silicone goo is unpredictable and gets crazy hot and either just dies and does nothing, or if you're really lucky blows it's little case up trashing your diff.

to the guy that thrashed the hell out of his car leaving the dealer and it "wouldn't go forward" don't be pointing fingers at the viscous it does virtually nothing in a straight line (unless you were doing a sustained 140mph powerslide) and if it died wouldn't effect the way the car drove really so you either F'ed a bearing right in the A, or something. Was it snubbing wouldn't go forward, or was the motor running and it just wouldn't go forward?