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r200 lsd broke in half


bryan01

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http://ziptiedz.blogspot.co.uk/2013/07/r2oo-lsd-ripped-apart.html    <--blog link for more description and pictures

 

i've got a 240z with an RB. She's got an r200 lsd from a z31 300zxt, 280zxt halfshafts, the old style welded modern motorsports companion flanges, and 240z stub axles. The entire rear end was replaced with techno toy tuning RCLA's, drop mounts, cross bar, mustache bar, 3/4" swaybar, gc coil over kit, sectioned housings, 400# springs in the rear, all new poly bushings, and 5way tokico's.

 

i'm running under 400 wtq with hoosier r6 dot slicks, 255's/45's in the rear on 9.5/17's.

 

it seems that the pretty finned differential cover failed, causing the diff and associated halfshafts to slam into the pretty adjustable RCLA's, taco'ing the entire suspension, shifting everything foward, finally pulling the driver's side shaft out of socket, and then out of the diff.

 

i *think* it's ultimately because of the massive amount of wheelhop i was experiencing during the run.

 

first of all, do you think this reasoning makes sence as far as root cause?

 

I initially thought the shaft or stub axle broke first as the 240z stubs are the smallest of the options (i do have 280 stubs ready to go in, but i'd need new flanges etc, it was on the list that seems to have grown) and the shafts would be the next in line as far as weak links, but the shaft seems to be in one piece, maybe slightly bent. I haven't pulled the stub yet thou, it may be bent via eyeballing it, but the wheel is still solidly attached to the car, not even wobbley while being towed at 5mph or so by the track support atv. that and the RCLA's bent forward, not inward, causing me to believe it was the diff that went first.

 

secondly, if the above is correct, how do you prevent wheelhop without moving suspension points and building in anti-squat?

 

I did some digging and to let you know, I *think* the tokico's were set on the stiffest settings, but i would have to go back and verify (won't be able to for a while as i'm traveling). I know I always joke about it, but would wider /stickier tires help with the car being as light, or as un-stiff, as it may be (it's stripped down to 2 seats and a steering wheel)? What I have seems to work on the street OK, but based on what happened, the tires were probably loosing traction on the street during boost and instead hopped on the track because of more than adequate track prep.

 

As a side note, the chassis has no body stiffening, and i *think* this may have added to the wheelhop. I'm imagining a floppy chassis driving down the track like a wet noodle with 4x more torque than it was designed for.

 

Would strengthening (over-frame rails, rear connectors, half or whole cage etc) make a difference with the lack of squat, traction, or amt of hop? I'm afraid of getting a flat cover for the r200, replaceing everything that was potato-chipped, and having the same wheelhop cause ...

 

Help....

 

Thanks

Edited by bryan01
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front mount is the simple solid arizona z mount, rear mount is poly bushed alum t3 mustache bar

Ok I was just reading about the r200lsd covers breaking with the solid mounts. With the solid mount it puts all stress on the cover and it breaks, no wiggle room, like with the stock rubber mount. I will see if I can find it.

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Ok I was just reading about the r200lsd covers breaking with the solid mounts. With the solid mount it puts all stress on the cover and it breaks, no wiggle room, like with the stock rubber mount. I will see if I can find it.

 

wow, that's interesting, thanks for the info, i'll check it out, let me know if you find it first... maybe switching back to the solid cover will hold it in the future, assuming i can stop the wicked wheel hop

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wow, that's interesting, thanks for the info, i'll check it out, let me know if you find it first... maybe switching back to the solid cover will hold it in the future, assuming i can stop the wicked wheel hop

Is the front differential mount damaged any? like it is cracked  or solid mount ripped out?

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Is the front differential mount damaged any? like it is cracked  or solid mount ripped out?

 

i haven't pulled the diff yet, it was litterally hanging from the front mount mount, still attached to the cradle, so i'm assuming it's not cracked, otherwise it would no longer be supported up front ... i would have to check to be 1oo% sure thou, i *guess* the diff could be just resting up front and against the driverside halfshaft, which *is* currently sitting on the passenger side rcla... but from what i remember it was still attached, twisting the cradle down, meaning the front mount is still instact

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I've got a spare open r200, assuming the gears are ok i can either use that cover or if there are other issues with this case now i can swap the carrier, but i'll let you know how it goes... i'm was debating on switching to an r230 setup ... still weighing the pros/cons

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Not sure if this is as much an issue, but may be contributing factor... The Tokicos dont like spring rates above 250#.

 

Mike

 

i guess the first step is to check the setting next time i'm back in town, what shocks do you recommend above 250? but i'll look into it, thanks

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I don't know, but I can help you speculate and perhaps you can figure it out by inspection.  I've been dragging an LS2/T56/240z setup with 435# tq for 2 years, and (I shouldn't jinx myself), nothing has broken yet.   I dump the clutch at 4000rpm when I launch.  I have burned up a clutch by trying to be gentle, so I since have determined to dump the clutch and let the tires do their job and so far, so good.  I have Z31T halfshafts which use a different style of CV joint from what I see in your photos (I went to your link, too).  I'm running 250# springs.  I have been constantly researching other folks on this site since I started my build in order to try to avoid breaking and here is what I've found.

 

Bias ply slicks are a good plan as driveline shock absorbers-you are running autocross/roadrace tires that have SUPER stiff, super thick sidewalls-as tires go they are pretty heavy and they are really more for lateral traction as opposed to linear traction.  They are the polar opposite of the bias ply slick which is super light, has super thin and flexible sidewalls, and I run them at 15-20 psi to make them even more flexible and shock absorbing.  I can fry my R6s or A6s at will, on any surface, you need to get rid of them until autocross day when you are gonna do some cornering.  With my slicks, I have to be in water to spin them.  I have had wheel hop twice-once in the burnout box and once at an autocross on street tires-and I got off it just as soon as I realized what was happening.  I think the trick to avoiding wheel hop is to avoid spinning.  At your power level, you should be fine with 8.5-9 inch slicks, but if you can fit them, I'd go to 10" slicks and be done with it.  It takes a little getting used to, driving 100+mph with airbags for rear tires, because the car kind of swims down the track, but I think it is worth it for me to be able to punch it with impunity.  jnjdragracing (second fastest ET on the forum) just snapped BOTH his axles after years of reliability with bias ply slicks-what changed?  It was his first time running drag radials-the very first run.  With bias ply slicks and an R200, he carries both front wheels half way down the track.  Your 60' times kind of suck (sorry to hit you when you are down), you have got to be spinning like crazy-if you have 400# of torque, you ought to be 60'-ing in the 1.5s or perhaps 1.6s.  I'm running 1.5s consistently with an occasional high 1.4, but I can't cut a good light to save my life so I can't take credit for being any kind of driver!  Your 60' times are what I would expect from a stock L24 with slicks, so something isn't right, right off the line-you aren't getting that power down.

 

Check your ride height-if you start too low, the axles are at a severe angle both at the hub and at the diff.  If at all possible, you want to start with the car up a bit, then to squat to straight under power.  Check your CV spline engagement-SunnyZ had a problem with his axle being too short and it jumped right out of the outer CV.  I would think that 400# springs would keep you from squatting too far.  Shoot some video of your car and watch for bouncing of the tail, squatting of the rear and wheel spin.  If there is not enough rebound dampening, that could contribute to your wheelhop, though I really think just not spinning via slicks will pretty well manage that.  My tires "chirp" on gear changes (I do lift off throttle for shifts), but they don't spin or hop.

 

Check that sway bar to ensure that it absolutely couldn't have hit the axle-that force could have translated thru the axle to the diff and broken the cover.  Check torque on all your driveline hardware-is it possible that one of the studs that connect the diff cover to the mustache could have loosened up, then caused a crack in the cover that propogated further.  I gave up my sway bar just to be sure it doesn't smack the axles-you can live without it.

 

Hope that helps-I hope I haven't jinxed myself for this weekend by opening my trap.  I'm gonna be working on my shock settings specifically using video to help me "see" the effects of the individual changes.  I'm hoping to get 20 or more passes Saturday night, hot lapping as traffic will allow.

Edited by RebekahsZ
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i guess the first step is to check the setting next time i'm back in town, what shocks do you recommend above 250? but i'll look into it, thanks

Funny, I'm running 450 / 425 springs on Tokicos and having no issues.

Jumpin curbs and stuff... (race track burms that is)

Edited by duragg
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bryan, the night u broke the track was not the greatest. Does ur car wheel hop all the time even on the street?? Our silver car never wheel hops on the street but on occasion will at Greer?? And trust me wheel hop is the worst thing on our cars you're going to have to figure that out or it will continue to break. Let me know if you need anything to get it back together when u get back in town

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i am in greer, if you need a regular r200 differential cover let me know..

Steve

 

Steve? I seem to remember tony i-can-tig-weld-anything smith talking about a buddy of his into z's as well, is this you?

 

I don't know, but I can help you speculate and perhaps you can figure it out by inspection. 

 

...

 

Hope that helps-I hope I haven't jinxed myself for this weekend by opening my trap.  I'm gonna be working on my shock settings specifically using video to help me "see" the effects of the individual changes.  I'm hoping to get 20 or more passes Saturday night, hot lapping as traffic will allow.

 

Thank you so much for detailed reply!, I'll walk thru it this evening

 

Funny, I'm running 450 / 425 springs on Tokicos and having no issues.

Jumpin curbs and stuff...

 

"Take it off any sweet jumps?"

 

i remember a while back on the BritishV8 forum that some guys ripped the 2 bolts out of their aluminum covers. They had very high horsepower engines in their Triumphs. They use the R200 short noses in them. This is a fix you may be able to use:

 

http://forum.britishv8.org/read.php?3,35516

 

Thats what i was imagining i might need, but it seems a bit excessive. I mean i've got some tq, but not THAT much. It seems that would only be needed for rock crawlers and the like, but maybe not. Is this normal for higher tq guys to have to do things simiar to this? It seems to be masking my issue of hopping down the track, but once that is fixed <how?>, if the case is still considered too weak and a failure point then i'll still have to do something... trade out for the flat r200 longnose cover? I'm not looking forward to having to beef it up like that.

 

bryan, the night u broke the track was not the greatest. Does ur car wheel hop all the time even on the street?? Our silver car never wheel hops on the street but on occasion will at Greer?? And trust me wheel hop is the worst thing on our cars you're going to have to figure that out or it will continue to break. Let me know if you need anything to get it back together when u get back in town

Shupee! ... The car doesnt hop on the street, it spins the tires (again, the same dot slicks) ... Your silver one is a 280z right? Isnt that a lot heavier and have a much stiffer chassis? Maybe that has something to do with it? I won't be back til the end of august, i'll let you know

Edited by bryan01
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bryan, the night u broke the track was not the greatest. Does ur car wheel hop all the time even on the street?? Our silver car never wheel hops on the street but on occasion will at Greer?? And trust me wheel hop is the worst thing on our cars you're going to have to figure that out or it will continue to break. Let me know if you need anything to get it back together when u get back in town

 

We'll have to get together though, I might have some compainion flanges for you... If you see a spare r230 lsd text me, I may go that route to get the car back on the road quickly when I get back

Edited by bryan01
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Solid front diff mount contributed to the problem.  Tokicos with poor rebound control at those spring rates are probably why you're gettign wheel hop.Wheel hop was the direct cause of the failure.  Solidly mount the diff and the mustache bar or use poly as the mounts.  Don't mix and match.

 

Funny, I'm running 450 / 425 springs on Tokicos and having no issues.

 

 

Then you aren't paying attention... :-)  They have very little rebound control with spring rates above 250. 

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