HowlerMonkey Posted December 17, 2007 Share Posted December 17, 2007 Tire stagger combined with a tight diff. Swap the rear tires with each other and see if it turns the other direction.........and sight down the rears and see if one is way off relative to the other to check for rear toe problems. Quote Link to comment Share on other sites More sharing options...
johnc Posted February 8, 2008 Author Share Posted February 8, 2008 Finally got to the bottom of this problem... and come to find out its not a problem. Some background: The Nismo R-Tune 1.5 Way LSD has three adjustments for preload - Low (51 ft. lbs.) Med (69 ft. lbs.) and High (101 ft. lbs.). Before the last even I had been running the diff set at Med which worked fine, except for a small push on corner entry, at the previous track events. For this Cal Speeday event I backed off the adjustment to Low to reduce the push and get the car to turn in a little better. At the track, the diff worked fine and the push was reduced. My 350Z is at Unitrax and they pulled the diff, tore it down, and inspected it. There's nothing wrong with the diff and its odd street driving power on/off behavior is the result of the design and me having the diff set on the Low setting. The best Unitrax can figure is that the combination of vehicle weight, engine torque, and differential design (ramps and preload adjuster) has the diff locking and unlocking randomly under part throttle. A lot of that may be because the preload adjuster is a poor design and doesn't appear to work properly on the low setting. They think it might be allowing 0 or 51 ft. lbs. of preload. Anyway, I'm going to pull that diff and sell it on eBay. Unitrax is installing an OS Giken Super Lock LSD in my 350Z: http://osgiken.net/products/superlock.html Quote Link to comment Share on other sites More sharing options...
JMortensen Posted February 8, 2008 Share Posted February 8, 2008 Interesting diagnosis. I would think that for the diff to be causing the car to go one way under accel and another under decel that it would have to be locking one wheel or the other, because if it locked both it wouldn't cause a move to either side in particular. I don't really see how that can happen in a clutch LSD. I have driven a broken 2 pinion Nismo LSD and had it locking and unlocking as I drove. The feeling was like the rear was shifting around side to side under acceleration. Other than that there were really no noticeable symptoms. It'll be interesting to see if the OS Giken unit fixes the problem... Quote Link to comment Share on other sites More sharing options...
johnc Posted February 8, 2008 Author Share Posted February 8, 2008 I agree and I still think there's more to the problem then what Unitrax and I have been able to figure out. But, its time for me to move on and get back on the track. Quote Link to comment Share on other sites More sharing options...
johnc Posted February 13, 2008 Author Share Posted February 13, 2008 Aaawww crap! New diff is in and problem still exists, although to a lesser degree. I think you guys who said it was a suspension issue might be right. I am swapping the CV shafts left to right as a test to see if they might be causing the problem. Now I need to get the car on a lift to disassemble the rear suspension. Quote Link to comment Share on other sites More sharing options...
proxlamus© Posted February 13, 2008 Share Posted February 13, 2008 aww man im sorry John! thanks for updating this thread as you go! always fun and informative to read the diagnosis and analysis Quote Link to comment Share on other sites More sharing options...
JMortensen Posted February 13, 2008 Share Posted February 13, 2008 There is a specific toe link on those cars right? That'd be the first place I look. Quote Link to comment Share on other sites More sharing options...
woldson Posted February 13, 2008 Share Posted February 13, 2008 Worst case senerio, guess something exotic and expensive, replace it and it ends up being something simple. Hope you find the issue with little more cost to you. Quote Link to comment Share on other sites More sharing options...
johnc Posted February 13, 2008 Author Share Posted February 13, 2008 I know. I'm guilty as charged. Instead of properly diagnosing the problem, I picked the most expensive part to R&R. I was just being lazy - a customer's car is on the lift and I didn't want to crawl under my 350Z in the alley behind the shop. Another lesson re-learned. Quote Link to comment Share on other sites More sharing options...
tube80z Posted February 13, 2008 Share Posted February 13, 2008 Do these cars use bushing compliance to control toe? I know some of the new mulit-link systems use rubber bushings that are very stiff in certain directions and compliant in others. It may be something as simple as that. For a test I'd take the wheel off and mount a long bar to the hub and lever it back and forth and see how much it moves. Then try the other side. It may help to pin point the issue. Cary Quote Link to comment Share on other sites More sharing options...
johnc Posted February 15, 2008 Author Share Posted February 15, 2008 Tire stagger combined with a tight diff. Swap the rear tires with each other and see if it turns the other direction.........and sight down the rears and see if one is way off relative to the other to check for rear toe problems. I am officially an idiot. Don't come to me for suspension questions ever again. Looking at the car I noticed: 225/40-18 on the right front. 245/40-18 on the left front. 225/40-18 on the left rear. 245/40-18 on the right rear. 10 minutes with a jack and a lug wrench solved the problem. A $1,300.00 lesson learned. God I'm an idiot. Quote Link to comment Share on other sites More sharing options...
blueovalz Posted February 15, 2008 Share Posted February 15, 2008 Uhhh....no John....you just were....ah........crossjacking some weight around...yeah, that's it! It happens to the best of us, (and for me, and even to the worst of us) as well. Last month I put the intake manifold on, and left the lifters out. Quote Link to comment Share on other sites More sharing options...
EMWHYR0HEN Posted February 15, 2008 Share Posted February 15, 2008 HAhahahahaha. Please tell me it was the 17 year old kid who works for you that put the wheels on like that.... Glad you solved your problem. Hahahahha Quote Link to comment Share on other sites More sharing options...
G.I.jonas Posted February 15, 2008 Share Posted February 15, 2008 :lmao::lmao:haha i'm lucky today.I cought a few funny threads that are making me feel better about myself.Hey at least you have some more sweet parts now. Quote Link to comment Share on other sites More sharing options...
johnc Posted February 15, 2008 Author Share Posted February 15, 2008 My only excuse, and its a pretty thin one, was that it was raining when I swapped the race tires for the street tires. Why I didn't notice the goof up during the two months of sunny weather since I made the swap...? I have no excuse. I'll be putting my perfectly good Nismo R-Tune LSD on eBay soon... Quote Link to comment Share on other sites More sharing options...
JMortensen Posted February 15, 2008 Share Posted February 15, 2008 We've ALL been there, still funny though... I'll be putting my perfectly good Nismo R-Tune LSD on eBay soon... You don't want to get another diff in a different ratio and be able to swap it out? Quote Link to comment Share on other sites More sharing options...
katman Posted February 16, 2008 Share Posted February 16, 2008 "God I'm an idiot." That's about how I felt watching one of my ITS cars at turn 12 at Road Atlanta lose the left rear wheel right in front of me. Uh, somebody forgot to tighten the lugs. I told the driver I used to have somebody on the team whose sole job was to manage wheels and tires and lugs, and if he wasn't so cheap that guy'd still be doing that- so it wasn't my fault! Shake it off ole buddy. Sorry it the lesson cost money. Quote Link to comment Share on other sites More sharing options...
woldson Posted February 16, 2008 Share Posted February 16, 2008 Dang that pretty takes the cake as a worst case senerio.... At least it did not take much to repair. Hopefully murphy will leave you alone for a while since he got his kicks out of you. Sorry again. At least you can rest assured no one would of guessed it;). Quote Link to comment Share on other sites More sharing options...
BillZ260 Posted February 16, 2008 Share Posted February 16, 2008 I'm glad to see some of Z greats aren't immune to whatever it is I tend to get quite a bit more often. Quote Link to comment Share on other sites More sharing options...
bjhines Posted February 16, 2008 Share Posted February 16, 2008 LOL!!! That is a good one. I am waiting for Murphy to hit me up for some lovin. I am getting my new 240Z track car close to completion and I fully expect to find some really stupid mistake that forces me to completely change some aspect of my modificaitons. Your $1300 booboo is still an improvement. Quote Link to comment Share on other sites More sharing options...
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