shaking while accelerating - worn inner joints?

[svizoman]

i have a fwd 6 spead manual and when in 5th or 6th gear with engine rpm under 2.5k (speed 80-100kph) and hit the accelerator i feel shaking. i was suspecting either clutch or dmf but when visited the dealer and went for test drive he said this is probably worn inner joints on a half shaft.

my only dilema with that explanation is why there is no shaking even at full throttle if you shift in 5th and 6th at higher engine rpm (above 3000). then car only accelerate hard and with no skaking.

as i understand half shafts are extensions from diff that acts as final gear ratio. and for them it does not matter which gear you use, but clutch on the other hand does feel higher torque at higher gears.
by my understanding if it is due to worn
inner joint it should shake even at lower gears and
troughout all engine rpms.

 

[RabbitGTI]

You have to get it on a lift and examine a lot of stuff. Motor mounts, CV joints, axle flanges, steering rack bolts, subframe bushings, etc....

 

[turbodieseldyke]

My shaking stopped after replacing the axles. The passenger side was so worn out, that when I stood it up next to the replacement axle, it was about 2cm shorter. The weight of the axle + outer end made the inner joint collapse into itself with no resistance. I assume the grease turned into oil, or disintegrated some other way, because the boot rubber was still intact and had no signs of grease leaking out.

It mostly vibrated in 5th/6th under load, at lower rpm (1500-2000), and never in 1-2-3.

It doesn't matter how you think the physics should work in these parts, they work or don't work in their own way that maybe defies explanation. There are other circumstances where wheels or bearings will vibrate at certain speeds or frequencies, but not others. I've read that physicists still can't explain how a bicycle can possibly stay upright and maintain balance and forward motion, so that's what "science" is good for.

 

[Lug_Nut]

The wear and the resulting play in the joint is most noticed when under high torque, about 2k rpm. Higher engine speed may have more power (twist times rate), but that is due to higher rpm. 5th and 6th are in use for a longer time, in that peak torque range, so boost can build longer. In lower gears you are into, then past, that 2k rpm range more quickly. You'll experience the same shake in 4th at full acceleration at 2k rpm when towing a trailer or climbing a hill.

In my experience the outer joint is more likely to have the greater wear. In either situation the axle has to come out to replace one joint so just replace both.

 

[RabbitGTI]

another clue is inner joint or flange shakes the shifter.

 

[oilhammer]

Yep, inner joints... usually the right side is the worst, as it gets cooked by the exhaust faster. Sometimes you can push some grease in there, move it in and out some, and buy some time.

 

[turbodieseldyke]

Yep, inner joints... usually the right side is the worst, as it gets cooked by the exhaust faster. Sometimes you can push some grease in there, move it in and out some, and buy some time.

I suppose one of these might buy some time too

Quick Question -- No axle heat shield

Folks, I was wrenching under my car most of today to repair my DPF system and in the process of fixing it realized... I have no heat shield on my axle. Is this normal or concerning, or is it just... a thing that's missing? I can run over to pick n' pull if I need to for it, but if it's moot...

forums.tdiclub.com