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Broken driveshaft for all you metallurgists out there.. https://ausmini.com/forums/viewtopic.php?f=23&t=40627	Page 1 of 2

Author:	Mini Mad [ Mon Mar 31, 2008 11:25 pm ]
Post subject:	Broken driveshaft for all you metallurgists out there..
For those of you that didn't see the thread in spotted i broke my driveshafts a couple of weeks ago about 2 days after it was registered. The story goes that after get used to how the car was behaving and a bit more trust that all was swell, i gave my sister a drive and she commented on how hard the clutch was so i told her "it is so you can do this" and proceeded to rev the car to around 3500rpm and popped the clutch (it's a 4puck ceramic button) which instantly killed the longer drivers side shaft This is the aftermath: So what do we think? just too much power? dodgy shaft maker? combination of both? don't say driver

Author:	Betty [ Mon Mar 31, 2008 11:28 pm ]
Post subject:
imy opinion - you should stop biting your nails

Author:	drmini in aust [ Tue Apr 01, 2008 6:39 am ]
Post subject:
Incorrect re- heat treatment of the Toyota shaft is my bet. That's the trouble with annealing (softening) then rehardening of Toyota or other OEM parts- how would anybody know the factory steel spec and original heat treatment used. Get some billets made, out of GOOD axle steel.

Author:	Archangel007 [ Tue Apr 01, 2008 8:10 am ]
Post subject:
Sheared it right off at its weakest point. My guess would be due to incorrect mode of operation!! In all seriousness, the shaft should have withstood that kind of treatment, my guess is, like Doc said, incorrect rehardening, or poor metallurgy. If its going to be subject to that kind of treatment, billet 4340 shafts would be the go!! Cheers, Tricky

Author:	clubmn [ Tue Apr 01, 2008 10:04 am ]
Post subject:	mm1275
it happened on my moke about 3 weeks ago. certainly not a power issue over hear, with the power my 998 is pumping out it could barely run a mixer.

Author:	smac [ Tue Apr 01, 2008 10:23 am ]
Post subject:
Soo...was it a modified shaft or not?

Author:	Mini Mad [ Tue Apr 01, 2008 10:30 am ]
Post subject:
These were the original starlet shafts from the frontcut - cut down (as they were too long) resplined and hardened again. A few people have gone this way without problems, but no one is running an LSD with slicks and a button clutch either..

Author:	borgy [ Tue Apr 01, 2008 10:49 am ]
Post subject:
Incorrect heat treatment or The cutting back of the original shaft is your problem.....

Author:	Blokeinamoke [ Tue Apr 01, 2008 11:02 am ]
Post subject:
i reckon you had a crack and in tune harmonic. Any wheel tramp at the time it failed?

Author:	Mearcat [ Tue Apr 01, 2008 11:40 am ]
Post subject:
What type of cost difference would there be in getting the stock Starlet shafts cut/resplined vs getting billet 4340 shaft made up?

Author:	minstar [ Tue Apr 01, 2008 12:21 pm ]
Post subject:
Funny that, mine has this setup and been on the road close to two years and no trouble. And my set of D01J are now bald after 5-6 months. However, I notice she seem to rev but not actually get there with the same urgency and have a strong feeling my clutch has gone. So I guess at these kind of power limits its one or another, still could have been your diff! Cheers M

Author:	Mini Mad [ Tue Apr 01, 2008 12:45 pm ]
Post subject:
Mearcat wrote: What type of cost difference would there be in getting the stock Starlet shafts cut/resplined vs getting billet 4340 shaft made up? Billet shafts you are looking at about $1000 and Cut and respline anywhere from $250+ depending who you go to. minstar wrote: Funny that, mine has this setup and been on the road close to two years and no trouble. And my set of D01J are now bald after 5-6 months. However, I notice she seem to rev but not actually get there with the same urgency and have a strong feeling my clutch has gone. So I guess at these kind of power limits its one or another, still could have been your diff! Cheers M I am pretty sure they may have not been hardened right. With your setup Matt, something has given in, this time it's your clutch, once you uprate that it will move along the line somewhere. Also i think you still have no LSD? and without LSD you have far less strain as all the power will go to one wheel right? I'm not too worried about the LSD letting go, it has a lifetime warranty - i think the next thing to go will be the CV itself or maybe the gearbox as everything else is non standard or uprated from the toyota part.

Author:	minimetoy [ Tue Apr 01, 2008 12:47 pm ]
Post subject:
Doc The place that re-hardened the shafts also did mine. The guy there actually tested the hardness of the shaft before it was treated. Josh's shafts have probably not been hardened correctly and that has caused it to give way. My shafts have copped a beating and they are still alive, however i don't have a LSD nor is my power the same as Josh's at the moment, we will see what happens in the near future.

Author:	9YaTaH [ Tue Apr 01, 2008 6:15 pm ]
Post subject:	Afters?
minimetoy wrote: Doc The place that re-hardened the shafts also did mine. The guy there actually tested the hardness of the shaft before it was treated. What about after treatment?

Author:	92 [ Tue Apr 01, 2008 7:27 pm ]
Post subject:
I have just been studying this sort of thing at college Looks like a brittle fracture shaft is too hard You can hardness test the shaft before hand but this doesn't tell you the make up of the steel so you can't really heat treat properly but you can make it the correct hardness so the spline doesn't ware. Should have a softer core and hard outside but looks hard all the way through. My billet shafts cost $400 to spline and heat treat I did the rest of the machining my self.The actual shaft diameter should be 5% smaller diameter than the root diameter of the spline to transfer the stress out of the spline and put it into the shaft and a nice radii in the transtion. Otherwise these shafts are a prime example of what happens in breaks in the spline.

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