What is this violent jerking in driveline?

gaboonviper85

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Jan 13, 2008
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IwantMKIII;1067347 said:
lmao, i don't know why i keep thinking its 35, btw im finding more and more im having wheel hop still on this chassis even with the new suspension :( looks like ill need some traction bars or something

you need to put in the other diff...and you probably need bushings like I do!
 

IJ.

Grumpy Old Man
Mar 30, 2005
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gaboonviper85;1067342 said:
Well... Ij can you find the pic I posted of what a fubar driveshaft looks like cause again I'm on my iPhone...

Adam...I saw this driveshaft before you installed it...your driveshaft is fine!

But this is what...I...think. The diff has major backlash (aka play)...the pinion gear and ring gear are worn out of spec....what this will do is.......while you accelerate at a decent rate and have a nice pull it doesn't jerk...BUT once you let off the gas it jerks and throws you forward...am I right?? This is a common problem in all old cars that have been beat to hell....basically your driveshaft acts like a torsion bar cause there is slop in the diff..

Adam.....put the trans in neutral and put the parking brake on....twist the driveshat in one direction then twist it in the other and how much twist could you get before it stopes?
Might have looked ok the day it was installed then moved under power the first run..

Can't see how backlash will make vibration on overrun that's usually either an out of phase shaft or damaged Uni joints.
 

gaboonviper85

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Jan 13, 2008
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IJ.;1067782 said:
Might have looked ok the day it was installed then moved under power the first run..

Can't see how backlash will make vibration on overrun that's usually either an out of phase shaft or damaged Uni joints.

he isn't getting vibrations....he is getting jerking back and forth
 

IJ.

Grumpy Old Man
Mar 30, 2005
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If it were backlash he'd get a clunk as it came onto the back of the teeth then the load would hold it there until he accelerated again.
(Diffs usually just whine badly)

Can't think of ANYTHING in the trans that would cause what he describes.

Out of phase shaft will do it as it winds up under overrun then snaps back and forth.

A trashed Uni will do the same.
 

gaboonviper85

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IJ.;1067799 said:
If it were backlash he'd get a clunk as it came onto the back of the teeth then the load would hold it there until he accelerated again.
(Diffs usually just whine badly)

Can't think of ANYTHING in the trans that would cause what he describes.

Out of phase shaft will do it as it winds up under overrun then snaps back and forth.

A trashed Uni will do the same.


Adam called me a few days ago saying there is a massive clunking sound comeing from the bar of the car LOL....I told him then it was the rearend and I'm telling him now its the rearend...I'm waiting for him to believe me.
 

gaboonviper85

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IJ.;1067870 said:
1st I've head of this...... :nono:

Can't diagnose a problem without ALL the info..

LOL I know...I just knew it couldn't be the ds cause I personally removed it from his old car and it was perfect....my old truck would shake the piss out of you if you were coasting at low speeds LOL...drove it like that for 100,000 miles still LOL
 

IwantMKIII

WVU MAEngineering
Jun 12, 2007
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well my brother and I just took it out to isolate a definate time period in which it happens. Again, I can't replicate this jerking while cruising, all I can tell you is it happens and when im barely on the gas, like 1-3% throttle via SAFC.

We took notice the jerking starts right around 1200RPM and down when coming to a stop. He knows this jerking and agreed it happens time to time in cars but not to this degree and not consistantly like this.

I havn't had a chance to check rotational play on the driveshaft yet. With family visiting, im trying to spend as much time with them.

If you'd like I could take a vid of it in and out of the car. In the car im sure you could tell the jerking going on by the movement of the camera and I just don't know how it looks from outside the car.
 

Poodles

I play with fire
Jul 22, 2006
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Oh, forgot to also tell you it could be something completely not related to drivetrain...

Like the TPS being out of adjustment and not goint to fully closed throttle...
 

Quin

Trans killer
Dec 5, 2006
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Poodles;1067981 said:
Oh, forgot to also tell you it could be something completely not related to drivetrain...

Like the TPS being out of adjustment and not goint to fully closed throttle...

He said it happens when he's at very light throttle, so I doubt that would be the problem. Wouldn't that also show up in RPM surging? If it's doing what I think it's doing it's definitely not motor related at all.

Diff clunking? Would have been nice to know that from the get go! :3d_frown: lol