Broken drive shaft

[Ultramaroon]

Originally Posted by NoHaveMSG

These also make terrible paper weights, what an awful product


Here is a good post on CS of the driveshaft. Shorter and fatter has a higher critical speed, so if I was a driveshaft shaft I should be good to 100k rpms

https://www.ft86club.com/forums/show...8&postcount=31

Aspect ratio is key. I think we're even there.

[NoHaveMSG]

Originally Posted by Ultramaroon

Aspect ratio is key. I think we're even there.

LOL.

[Uplink]

Not to revive an old thread but bringing a discussion from the Crank Pulley thread back here.


I bought my first DSS aluminum unit back in 2015 and installed it at 4,633mi on the clock. It's now 2024 and I just cleared 66k this week. Aside from the driveline clunk/rattle at low speeds, this has been a phenomenal part that has seen commuting, Auto-X, and hard track driving. I did notice that with the thicker flange, you really should be using at least 5mm longer bolts to have a little extra bolt past the end of the engagement. The factory bolts just barely engage the nut fully.


Fast forward to 2 months ago, I picked up another DSS aluminum unit for a second FR-s and noticed this giant sticker on the shaft with a warning not to exceed 130mph. That was NOT on the original unit so I don't know if they are acknowledging the limitations of the part now or if the parts are made less robust. Either way, having a MPH limit instead of a RPM limit makes absolutely no sense. Depending on your gearing and tire size, the RPM the shaft spins at could be wildly different at 130mph. I guess that's just the safest way to mark it since most people won't do the engine vs shaft calculation.


It was a little disheartening to see that, not that there's currently much chance to get that fast with the car, but still. Having say a 150mph limit would give a nice reassuring buffer.


As for the CF driveshafts, I've had 2 of them go bad on my Vette leaving me stranded (once at the top of the VIR esses and once at Auto-X). Both times it was the epoxy that held the shaft to the aluminum yokes that went. This breaks down over time/stress/heat cycles and will let go without warning, letting the yoke spin free and unravel the shaft ends. Yes, it is a more graceful breakdown (feels like your clutch is slipping and power isn't getting to the wheels) so you save the risk of destroying your undercarriage and any nearby components, but it still fails and according to the manufacturers will go in time, not might go. Most race parts like this are considered consumables and are maintained/replaced every few seasons anyway, but I'd still steer clear of the carbon ones unless you're looking for every last bit of performance and cost isn't a concern.

[blsfrs]

At least you didn't learn the hard way like I did. I'm surprised it took DSS this long to warn customers about the limitations of this product.

[NoHaveMSG]

Yeah mine vibrates bad at about 115 with 4.30 rear end.

[Ultramaroon]

stock FTW

[gpvecchi]

I'm going with ZN8 one. It seems it gives decent results. 1.1 kg lighter and CV joint.

[StraightOuttaCanadaEh]

My aluminum DSS driveshaft vibrated bad at about 85 mph. Tried mounting it every which way but nothing helped. I don't know whether it was the solid engine mounts or all the diff/subframe bushing inserts.

It's a real shame as I enjoyed the absolutely sublime shifting with a one piece driveshaft. I'm kinda tempted to try again as the one I bought was second hand but they're SO expensive now.

[Grady]

Research drive shaft critical speed. Something you can not get around. I have the Verus CF shaft and it starts to resonate around 130. It is balance at the speed it would be turning at 160 but once installed it does not matter. This is not an issue for me since the tracks around here are short and I am just getting to over 110 on the longer straights.

[StraightOuttaCanadaEh]

Originally Posted by Grady

Research drive shaft critical speed. Something you can not get around. I have the Verus CF shaft and it starts to resonate around 130. It is balance at the speed it would be turning at 160 but once installed it does not matter. This is not an issue for me since the tracks around here are short and I am just getting to over 110 on the longer straights.

At 130 would be great since I'd never reach that speed but at 80 it was very intrusive making me think there was something inherently wrong with that unit.