driveline vibration TE71

[teun]

Men!

Over the past month or so, I've noticed a drive line vibration which becomes worse at highway speeds. The vibration doesn't occur on a certain amount of revs in all gears, mostly at highway speeds. The vibration can also be felt on deceleration, this does happen in more gears but not on a certain rpm level, it feels more related to speed.

More info;
- 5 link is all in new PU bushings. (recently put in, vibration was there before)
- I've cleaned the drive shaft
- U-joints have no play
- shaft doesn't move more than a mm up, down or sideways
- no excessive backlash as far as I can tell
- alignment is ok and it doesn't feel like an alignment issue.

Next to that, I haven't changed the motor and trans mount from new. Gear stick does shake a bit.

Could worn motor mounts be the culprit here?

thanks,

[Ivan141]

If it's speed related as you say I would guess it is an imbalance of the drive shaft. The shaft always has a rotation speed relative to the car's speed.
Guy I know had a similar problem with a DIY welded drive shaft, and it ended up ruining his input seal on the gearbox after a trackday.. There's a drive-shaft specialist shop (Avim) in Rotterdam Zuid that could do this for you.

[teun]

Thanks Ivan.
Any idea of the cost of something like this?
Also, removal of the shaft seems straight forward. the 2 center bearing bolts and the 4 before the diff and then pull it out?

[jondee86]

Two-piece driveshafts must be phased like this...



... otherwise you will get vibration. Make sure yours is assembled correctly.

Cheers... jondee86

[Ivan141]

I think it will be somewhere in the <50 euro range, but you could just give them a call or a visit to find out. I had a driveshaft shortened and rebalanced there for ~100 euro a few years ago. They did a nice job.
Couldn't hurt to check all wheels for bearing play while your at it.. a driveshaft wouldn't go out of balance gradually, but it's not unthinkable that a balance weight may have fallen off, causing a sudden high speed vibration.

[Ivan141]

jondee: interesting fact to know, but that could only happen if you take the shaft apart and reweld it right?

[teun]

Just took a drive specifically to check for this issue.
The vibration is under strong load at certain speeds (not distinct engine speeds)
It's stronger on decelleration and it becomes much less if I add or takr back a little bot of throttle.
It also seems like it's juttering a bit at low engine speed and low throttle. (I can hear it vaguely from the gearbox.

Does this give you guys any clues?

[jondee86]

Thanks to the wonderful AEU86 archives, I found this...



There is a square flange that you can see, that gets taken apart when
changing the hanger bearing. AFAIK it is possible to assemble that flange
90 degrees wrong i.e. out of phase.

Cheers... jondee86

EDIT: And you also need to check the hanger bearing is not loose and
flopping around. Grab the driveshaft next to the hanger bearing and push
pull vigorously. The rubber should hold the shaft firmly with not much
movement. If the rubber is perished/broken and the shaft moves 20mm
up and down, you need a new bearing.

[teun]

Thanks Johndee,

The shaft has not been off the car for the past 30 years of life, so I doubt it has been put back wrong.

I've checked the hanger bearing already when I was cleaning my shaft (this sounds dirty), it didn't move a bit. I'll check more vigorously today.

Since the vibration has been slowly worsening, would it be the shaft or should I look somewhere else?

[jondee86]

teun Wrote:Could worn motor mounts be the culprit here?

It's possible. While you are under the car take a tire lever or similar tool
and use it to lift the back of the gearbox a bit. Examine the mount rubbers
for breaks, softness from oil etc. Then do the same for the engine mounts
looking for excessive movement.

Driveshaft vibrations are notoriously difficult to diagnose. All the rotating
parts from crank pulley to rear axles are coupled together into a single
system, and the vibrations can be caused by anything from engine firing
pulses to an out of balance rear wheel.

Engine induced vibration can usually be eliminated by pushing in the
clutch and selecting neutral (or coasting down a long grade). If the
vibration remains, it is not caused by the engine. Wheel vibrations can be
isolated by swapping the front wheels to the rear axle. If it can be done
safely, raise the back of the car, put the rear axle on jackstands, chock
the front wheels and run the car in gear. Slowly increase the speed while
watching under the car to see what starts to shake.

The driveshaft itself can be bent, universals seized, hanger bearing loose
or seized, flange bolts loose, or as Ivan said, a balance weight could have
fallen off. If close inspection and vigorous shaking to detect any slop fails
to find a reason, then probably getting the driveshaft re-balanced would
be the next step.

Cheers... jondee86