Is something wrong with my LSD??

280z/300zx

So a little background. Back in 2009 when the Z first hit I special ordered a touring sport 6-speed. Loved the yellow color, it was my graduation present to myself for med school as some here know. After a year and half she was sadly totaled. Replaced her with a 2010 Nismo since ordering a 2010 replica in blue would have taken 3mo. I've owned RWD since I was 15 starting with an S14, then a toyota mini truck, then my 84 300zx (still own), and my 77 280z (still own). Not that I'm proud of it but I'm no stranger to both legal and illegal drag racing (I no longer do this). I also started auto-x 2 years ago. I'm not a professional driver by any means but I'm no stranger to appropriate technique. I also have experience with V8's via 2000 Trans Am, C6 Vette, and the new LS3 Camaro thanks to my girlfriend.

So here is my problem, my Nismo won't launch straight. It almost seems as if it has an open diff instead of an LSD. I've never felt like I could truly enjoy my car because the moment I try to get on it from a stop or coming out of a turn she loses grip more than I'm used to. I think the best comparison is my 09 370z obviously. In that car traction wasn't the greatest with the stock tires but the car at least stayed relatively straight if you gunned it from a stand still or dropped the clutch. Ton's of wheel hop, but straight. Lately it's been bothering me and I've been doing a lot of searching here. I've also been youtubing amateur racing videos of 370z's for observation. So today I decided to do a few test launches to try and figure out technique but couldn't nail it down

So if I do a simple launch at 1500-2000 rpm and feather the clutch out only applying 1/3 throttle the whole time the car will go sideways with the back end coming out for probably 10-20ft. I'm fighting the steering wheel trying to keep the car pointed straight. Finally the car hooks but as soon as I put my foot into it the tires spin. At about 5k rpm the tires stop spinning and I'm good. Once I hit 2nd gear though the back end wants to come out again. It's only for a split second but you can feel it's very unstable. I've done done rolling 1st and rolling 2nd gear launches where you just put the foot down. In both gears the back end will come out, even rolling.

Now I had similar problems in my 280z once I started adding too many mods and once I swapped in a LSD it went away. Again, my 09 370z never acted this way, it was still bad with traction, but it didn't pull sideways. My girlfriends 2010 Camaro is a blast. You can drop the clutch at any RPM and it just burns and goes no problems. Same with her old C6 Vette.

Sorry it's so long but I'm just trying to figure out if something is wrong or what. I haven't even taken it to the drag strip since I've bought it because I know I'll run horrible times. I only did one auto-x event and I was all over the place. Contrast my 09 370z saw several drag and auto-x events. My first thought is flushing the fluid per the DIY. I'm also considering replacing the tires prematurely or RE11's. So opinions please. Flame suit is on but I'm thinking something just doesn't seem right, but maybe it's just me.

L33T Z34

I assume this Nismo is all stock w/the Yoko ADVAN sport tires and the crappy viscous LSD? The viscous probably heated up after the first couple "beatings" when you were testing and basically it acts like an open diff once it's hot.
My suggestion is install a 1.5 way clutch LSD and some RE11s or ADVAN AD08s. Also, to get rid of that nasty wheel hop look into installing SPL solid rear differential mounts and SPL rear traction links.
Here's a post on how to upgrade the rear differential.

NitrousZ34

I would say change out the fluid like you were going to do and try that and see how it is. Are you trying to launch on a bumpy or uneven road? The stock LSD is pretty horrible so like L33T said, maybe its just hot and isnt working properly. Is your Nismo pretty heavily modded?

SS_Firehawk

After about 50k miles or so, the stock diff is worthless... more worthless than it is new that is.

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Osiris

just curious, but when you're car lost traction, did it tend to kick out the back end the same direction each time?

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280z/300zx

Well I don't think it's overheating because it did it on the 1st launch. Basically on my way home today I pulled off to an empty side street near an industrial area where there is no one. Only did 5 pulls. The drive time from work to this area was about 15min. Didn't do anything crazy on the drive over, just normal driving.

As for road conditions, not bumpy at all. Had a slight lean to it going from the higher left to the right, however the car always pulled left.

Also I should say this isn't the first time I've experienced this. There was an incident last year against a Z06, I'll just leave it at that, where I experienced the same problem. Had to shift into 2nd by 4k rpm and even in 2nd I let off half way through because I was sideways. I've also experienced the same thing at the start line of our auto-x course the one time I went. I usually just rolled out of the start and went into 2nd immediately and kept it there the whole run.

As for my car, from the first week of ownership I put on FI 18" CBE. This was the same exhaust from my 09 touring sport that I just swapped over. It did make a difference powerwise but nothing crazy to cause traction problems.

I thought about swapping diffs but honestly I'm probably going to be trading in the next year or two so not sure it's worth it. With the new C7 Vette coming, the next gen STI, and of course the next gen Z I'll probably be moving on from the 370z. So not sure it's worth the hassle of swapping diffs, not to mention here in Vegas there is only one place that can do it and I'm not sure I have full confidence in them.

I guess I'll try a fluid change in the next week or two and go from there.

Osiris

Same here...ended up on side of road because of it.

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SS_Firehawk

LA is only 4-5 hours away

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2011 Nismo#91

I don't think the diff fluid is a serviceable item, I think it's sealed and you need to replace it. I don't know what would cause this issue so early as someone had mentioned the diff fluid should only break down after a couple of launches not the first and takes imo 30k+ miles to break down.

It should be under warranty but how would you go about diagnosing this issue with out the dealership actually launching your car.

280z/300zx

There is a DIY for how to change the diff fluid. No different than any other diff made 40 years ago. In fact the 370z is exactly the same as my 1977 280z; only difference is the amount and type of fluid used.

I would agree though that the fluid shouldn't be broken down at the mileage I'm at but I've read a few posts where people changed the tranny fluid or diff fluid prematurely and actually noticed smoother, crisper shifts as well as less vibration and noise. For the cost of the fluid and a little of my time I'm willing to give it a shot. Tires will be next but it just seems odd to get so much uncontrolled wheel spin from a car with so little torque vs. tire width. I mean tell me, does your 2011 Nismo go sideways when you launch it or does it stay straight and you take off no problem?

BGTV8

I suspect that what you are getting is massive wheelspin because the diff is actually working.

Torque reaction will be at 90-degrees to the line of thrust and if the diff is rooted (Oz-speak for worn-out) and only one wheel is spinning, then the non-spinning wheel will tend to keep you straight.

If both wheels cut loose and all the tyres are doing is spinning, the torque reaction will tend to push the rear of the car sideways.

Sounds like the car is grip-limited at the rear on a hard launch and the fix is to provide more grip - better rear tyres will help, as will a less aggressive launch.

I have a MY09 OZ-spec Z34 with a Quaife diff - currently fitted with Nitto NT05s for daily use and NT01 fr track-work and with traction control off, hard launches will fry the rear tyres, so throttle moderation gets me off the line quickest (circuit work rather than 1/4 mile). I also have to make sure that the tyres are warmed up on the out-lap before leaning on the car - if I don;t do that, then it is instant oversteer.

If you launch hard, are you leaving rubber on the road from both sides of the car - if so, the diffis working as designed and I am maybe right - if only one wheel is spinning, then I am wrong and it is a different problem ...

A car that steps out on a hard launch is definitely grip limited though ....

RB

280z/300zx

Thanks for the well worded and informed replay. What you are saying makes sense it's just that when I've watched vids of other 370z's launching they don't do this. Also when I did launch the car it was far from hard. I don't doubt the stock tires suck for traction but with 7/32's still left of them I would think they would do better than they are. Thanks though for your replay. I'll ponder this a bit more.

SS_Firehawk

My fathers Cayman S steps out like what you describe and his vehicle does not have a diff.

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DarkJak

Noticed this today, I have 15k miles and the car's tail always goes the the right on a launch.

Tazicon

The stock tires are crappy and it is so easy to spin them, I am assuming you have the stock potz on still correct? My car does the same stuff and its an auto. I have to feather the gas to get a good launch. One thing about Vegas is the asphalt is slick to begin with, sticky tires are a must and the stock potz just hook up. I can get it side ways real easy.

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