Z-Gad Posted December 12, 2006 Share Posted December 12, 2006 I already posted something in the motorsports section of the forums, but figured that not everyone would see the photos... Anyway, here is the background. I was at the dragstrip, did a good burnout to heat the tires, brought my rpm's up to around 3000, hit the nitrous, held the brakes until the lights came down, and launched at roughly 5500 rpm's at 20+ lbs of boost and the 100 shot on top and blammo!! These are a few photos of what happened... http://album.hybridz.org/showphoto.php?photo=12134&cat=500 http://album.hybridz.org/showphoto.php?photo=12136&cat=500 http://album.hybridz.org/showphoto.php?photo=12135&cat=500 That was definately the hardest I have ever tried launching the car. Here is my setup for those that are unfamiliar, I run a solid diff mount (from MSA) in the front and urethane bushings on the mustache bar. I have a 3.36 R200 LSD, Z31 300zx turbo CV"s, and Ross' CV adapters on stock 280z stub axles. As far as I can tell, the front diff mount pulled up through the front support bar... shown here http://album.hybridz.org/showphoto.php?photo=12199&cat=500 .. then broke the rear cover from the diff (bolts were still attached to the mustache bar), the diff torqued to the right, destroying the driver's side CV. OK, there appears to be no damage to the differential itself (just the cover), no damage to the passenger's side CV, and the mustache bar is not broken either. The driveshaft required a new u-joint... no biggee. I know it could have been much worse. I never even considered that the front support would fail like it did, so I figured I'd better put this over in the drivetrain section, just in case the info is of use to others instead of having it buried in a Motorsports thread about Orlando. I intend to reinstall the R200 for the time being, reinforce another front support prior to installation, while I decide on my next course of action for the rear end. Pax, Mike Quote Link to comment Share on other sites More sharing options...
Guest 280ZForce Posted December 12, 2006 Share Posted December 12, 2006 wow...surprised everything has even held up as long as it has with that monster you've built. Now to build that rear end up even better! Good luck on the fix, doesn't seem too bad...but just wow. Quote Link to comment Share on other sites More sharing options...
Pop N Wood Posted December 13, 2006 Share Posted December 13, 2006 Z Gads!! That's impressive! Expensive too. Looks like you were still running the original R180 cross piece that came with your 72. The later R200 pieces are significantly heavier. There also looks to be significant rust on the inside of that piece. What type of tires were you running? How long have you had the solid front mount and how many launches do you figure it had on it? We have had a lot of threads about fatique cracking with a solid front mount and flexible rear mount. Sounds like time to do the Ron Tyler front diff support. Maybe Ron was right about that 1/4 plate...... Quote Link to comment Share on other sites More sharing options...
Z-Gad Posted December 13, 2006 Author Share Posted December 13, 2006 Yepper - I have read some of the threads on the Ron Tyler mount. It was the old 71 240z piece. I have a later model one to replace it, but didn't even think to look at the differences between the two. I have had the same front mount for a year and a half with probably over a 100 launches on it. I do not see any fatigue/stress cracks on it either. Tires are Mickey Thompson ET Streets 26x11.5x16 with ~12 psi tire pressure. Quote Link to comment Share on other sites More sharing options...
fastzcars Posted December 13, 2006 Share Posted December 13, 2006 Well ,now you have an excuse to make the ron tyler mount ! Geesh!!! what torque you have!!!! Oh one more thing, now we know that the R200 can take a beating. Quote Link to comment Share on other sites More sharing options...
BayAreaZT Posted December 13, 2006 Share Posted December 13, 2006 Jeez, thats some impressive damage. You must be proud Quote Link to comment Share on other sites More sharing options...
speeder Posted December 13, 2006 Share Posted December 13, 2006 Carnage like that is both fascinating and horrifying - You are simultaneously proud that your raw power can destroy things but bummed because you have to go back "into the breech" and fix the latest weak link - Not to mention spend mo' money. Sure does make a good case for the top-supported front diff mount designs. Quote Link to comment Share on other sites More sharing options...
buZy Posted December 13, 2006 Share Posted December 13, 2006 I think you may need a live axel with all that power. Woah!... Or this trapped from top and bottom. Quote Link to comment Share on other sites More sharing options...
jnjdragracing Posted December 13, 2006 Share Posted December 13, 2006 Thanks for the info, We will be looking closely at our setup. Sorry for the mishap and glad all is okay. It looks like the Ron Tyler setup is the way to go. I will pass this info to my brother Jerry. Need to get it back together, March is approaching fast. John Quote Link to comment Share on other sites More sharing options...
blueovalz Posted December 13, 2006 Share Posted December 13, 2006 I see the mustache bar in the photo. Can I correctly assume that the front mount was solid and the rear was rubber or urethane? Quote Link to comment Share on other sites More sharing options...
Z-Gad Posted December 13, 2006 Author Share Posted December 13, 2006 I see the mustache bar in the photo. Can I correctly assume that the front mount was solid and the rear was rubber or urethane? Yes, front was solid and rear bar had urethane mounts. Quote Link to comment Share on other sites More sharing options...
bjhines Posted December 13, 2006 Share Posted December 13, 2006 We have been over this many times.. Front solid rear flexible mounting is bigass badass NONONO.... I'll say it again.. The people who sell the solid diff front mounts should be SHOT!!! they are Gaurateed to fail eventually... I have one that went to pieces with less than 200 HP and NO HARD LAUNCHES... Again.. DO NOT USE SOLID DIFF MOUNTS.... Quote Link to comment Share on other sites More sharing options...
blueovalz Posted December 13, 2006 Share Posted December 13, 2006 So true. As much as this has been discussed, it surprises me to still see it in practice, especially on the high torque applications. Again.. DO NOT USE SOLID DIFF MOUNTS.... UNLESS it is ALL solid. The half-and-half stuff is a recipe for failure, whether it's motor, transmission, or differential. Quote Link to comment Share on other sites More sharing options...
MONGO510 Posted December 14, 2006 Share Posted December 14, 2006 The Mustache Bar should be reinforced also! It will flex a lot under load! With a solid front you want rear to be solid too. Quote Link to comment Share on other sites More sharing options...
bjhines Posted December 14, 2006 Share Posted December 14, 2006 Ohh yes.. The Solid rear mount will allow the use of the solid front mount... Those Arizona Z-Car parts are absolutely STUNNING... but there are other home fabricated options... The little solid front mount is only part of the mounting system it was designed for... Vendors like Arizona Z-Car make the entire front and rear mounting system... Those are the way to go.. but don't blow your $40 on just the front mount and think it is going to help in the long run... Quote Link to comment Share on other sites More sharing options...
Z-Gad Posted December 14, 2006 Author Share Posted December 14, 2006 I have run a solid diff mount and urethane bushings on the mustache bar on all 4 of my Z cars over the last 10 years without any issues until now. Two of 240z's were n/a, my 400 hp 77 280z turbo 5-speed, and currently the 700+ rwhp 2JZGTE 240z and even now, the solid mount and urethane bushings were not the issue (as they are still intact), it was a lack of reinforcement of the stock front support. I understand that some have had issues, but alas I have not. Quote Link to comment Share on other sites More sharing options...
Pop N Wood Posted December 14, 2006 Share Posted December 14, 2006 the solid mount and urethane bushings were not the issue (as they are still intact), it was a lack of reinforcement of the stock front support. Well, no, they are the issue. Something has to flex, and by using a solid front mount and flexible rear mount means the flexure HAD to happen in the steel of that almost 40 year old cross member. I would be willing to bet if you magnafluxed any of your other crossmembers you will find some level of stress cracks on at least some of them. Actually you are getting to the level of performance where normal rules no longer apply. JohnC once posted the preventive maintenance he did on his race car between each race and on a yearly basis. Might be a good idea to do something similar with the beast you have. On the up side this answers the question we had on another thread about whether the diff is subject to twisting along the car centerline. I wonder if you had a functioning arrestor strap if it would have saved the back of your diff. Quote Link to comment Share on other sites More sharing options...
Z-Gad Posted December 14, 2006 Author Share Posted December 14, 2006 Well, no, they are the issue. Something has to flex, and by using a solid front mount and flexible rear mount means the flexure HAD to happen in the steel of that almost 40 year old cross member. I still don't see them being the issue here, I mean, if the front member had been reinforced, would it have happened at all? Quote Link to comment Share on other sites More sharing options...
stony Posted December 14, 2006 Share Posted December 14, 2006 I tend to agree with ZGAD it looks like the failure on this one was the front mount pulled out of the front member, then that caused the diff housing and all the other damage. But then again the rear mounts not being solid mounted may have caused movement in that front mount weakening it over time and resulting in it pulling thru. ZGAD thanks for the PICs Sorry over the breakage BUT i was really starting to get bummed over the route i took on backhalving the car after seeing your car run. But now i dont feel so bad... if anything for safety reasons that would have sucked if it that let go like that at 1/2 track. Quote Link to comment Share on other sites More sharing options...
Pop N Wood Posted December 14, 2006 Share Posted December 14, 2006 I still don't see them being the issue here, I mean, if the front member had been reinforced, would it have happened at all? Well, possibly yes again. If you repeatedly bend a piece of metal back and forth it gets work hardened. That makes it brittle and prone to cracking. The solid mount is what caused the crossmember to get hard and crack. Solid mounting the rear would have help limit the motion and possibly prevented the front from going. But regular inspections might have discovered the degradation before such a catastrophic failure. Quote Link to comment Share on other sites More sharing options...
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