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DRIVESHAFT TECH IN CHIT CHAT WANTS: 74'' 7K RPM

xr-nut said:
It starts the shaking north of twenty and its bad enough by 40 that we turned back around. thanks, hopefully we get it sorted. I'll be taking a c5 off the front line if not. :laughing:
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Given the low speed onset,

anyway you can put this on stands and run it at idle speeds? I suspect with as bad as the vibes are, it will be visually obvious where the problem lies. Stands under rear axle, son in drivers seat with foot over brake. No fancy electronics that need to be shut down for this to happen? (our ABS and traction control have to be told the car is running while stationary)

low enough that I don't think I would start with the carrier bearing as cause, much more likely this is a phase issue on driveshaft ujoints

totally unrelated, but in early versions of the AMG, one team was chasing vibrations issues, the shaft between motor and transaxle, that runs in the torque tube had been incorrectly fabricated with ujoints out of phase. Was never caught in production, and they only found it because they had just done a clutch on another GT4 and the tech thought something looked odd with the driveshaft. You sure hope your driveshaft shop gets stuff right, but if the OEM can screw up, then ......

Assuming you have given the pinion a good shake, or it was good when run last with the one piece shaft. Same with tranny output? nothing feels loose when installed? sure you have covered all these bases already.

If this was higher speed there are a host of other suggestions, but low speed sure points to something "major" wrong.
 
XtremeJ said:
Given the low speed onset,

anyway you can put this on stands and run it at idle speeds? I suspect with as bad as the vibes are, it will be visually obvious where the problem lies. Stands under rear axle, son in drivers seat with foot over brake. No fancy electronics that need to be shut down for this to happen? (our ABS and traction control have to be told the car is running while stationary)

low enough that I don't think I would start with the carrier bearing as cause, much more likely this is a phase issue on driveshaft ujoints

Assuming you have given the pinion a good shake, or it was good when run last with the one piece shaft. Same with tranny output? nothing feels loose when installed? sure you have covered all these bases already.

If this was higher speed there are a host of other suggestions, but low speed sure points to something "major" wrong.
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Yes we can put it on the ground on stands and watch it. I'll try that first. no electronics, this truck is old. :laughing:

No it didn't have any issues last time I drove it with the one piece. in fact, if we cant sort this I'll cut out the carrier mount and put the one piece back in for sorc.
 
xr-nut said:
Yes we can put it on the ground on stands and watch it. I'll try that first. no electronics, this truck is old. :laughing:

No it didn't have any issues last time I drove it with the one piece. in fact, if we cant sort this I'll cut out the carrier mount and put the one piece back in for sorc.
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and worst case step down a class or two speed wise if that helps
 
xr-nut said:
It starts the shaking north of twenty and its bad enough by 40 that we turned back around. thanks, hopefully we get it sorted. I'll be taking a c5 off the front line if not. :laughing:
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Something is seriously fucked up with that shaft if it's that bad at such low speeds and I doubt it is anything you have done. I have seen some real janky shit in buggies and 4x4s that break every rule in the book that don't vibe like that.
 
grumpy356 said:
Here is the thread derail.

Growing up, my best friends dad, who was a great guy, RIP, had some pretty messed up teeth.

The story came up one night as to how his mouth got jacked up.
He was working under a car and dropped the driveshaft in his mouth.
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My father in law was trying to turn a tractor pto with a pipe wrench and his helper hit the starter. That knocked his front teeth out :homer:.
 
redneckengineered said:
Something is seriously fucked up with that shaft if it's that bad at such low speeds and I doubt it is anything you have done. I have seen some real janky shit in buggies and 4x4s that break every rule in the book that don't vibe like that.
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this.

the anal level of getting things within 1/2° to-the-book to get it to turn smoother at 100+ mph and the 20 mph vibration to violent shaking at 40 mph are 2 very different things.

I lengthened a front drive shaft on my XJ by to cut right in half, weld back together to not be at max extended in rear after the SYE install & 6.5" lift kit.... with AC Lincoln tomb stick welder when I was 19. No issue going 50+ to/from trailheads.

assuming no ridiculous runout when spinning (as if they did not see it and balanced it out by putting all of weights on one side).

I think a botched balance job. I will cut some weights off or tape weights on and try see whether there's improvement (or worse) by spinning on on jack stands if all efforts were exhausted elsewhere if I am in your situation, to diagnose.
 
Not saying it is or isnt. But I can make a driveline do that on my balancer just by having too much weight/not enough, in the wrong spot or things not being quite straight enough. Spins fine up to whatever rpm and then it looses its shit.

Put your video on slowmo. That thing sure looks like its gotta bobble in it from the start.
 
CarterKraft said:
She pissed....
Front yokes same as before or phased 90?
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no, we rotated the them 90deg, i'll put it back and run it again on the stands.
XtremeJ said:
Well there is your vibration
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I think it has a wobble from the get go.
Steve300xcw said:
Not saying it is or isnt. But I can make a driveline do that on my balancer just by having too much weight/not enough, in the wrong spot or things not being quite straight enough. Spins fine up to whatever rpm and then it looses its shit.

Put your video on slowmo. That thing sure looks like its gotta bobble in it from the start.
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I saw it in real life. i'll slow it down and watch again.


whats causing that? It doesnt do it with the rear shaft out.
 
xr-nut said:
whats causing that? It doesnt do it with the rear shaft out.
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Hard to say. Put an indicator on the shaft coming out of the carrier and see what it says. Check the rear tube as well. I bet you'll find something.

I generally need the driveline to be at or under .005" before I can balance it. With a 2 piece they can sometimes be finicky and the actual problem is not where you think it is.

Really wont know much until its on a balancer though.
 
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xr-nut said:
there you are! where you been hiding buddy? :laughing:
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I dunno anything about driveshafts, I shorten them with a grinder and welder, and when they vibrate I toss a couple hose clamps on them to try and get them balanced better
sometimes it even works, other times I just say "eh close enough" and deal with the newfound 65mph speed limit

p. much you're on your own, we can't hold the anglefinder for you
 
If you are getting .006-.007 under the truck, I'd say thats pretty good.

Is that the back shaft too?
 
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