Vibration thread #463

[choppo]

D2a auto td5 '03. Have a weird vibration at 89km/hr. By weird i mean;

Only happens at 89km/hr + with throttle applied. Replaced front shaft with a Tom Woods to no avail.

What has me buggered is it has something to do with throttle input i.e. driving at 89km/hr all good. Accelerate to 95km/hr a high frequency vibration occurs. Like an out of balance wheel, but no feedback through steering. So back off to 89km/hr all good. Get to a decent decline and the car coasts to 100km/hr NO throttle.... NO vibration. If i place the slightest hint of throttle, and i mean the slightest hint of throttle, not even accelerating down the hill it vibrates again. Foot off throttle and coast at 100, no vibration. Touch throttle, vibration.

Additional info: doesn't have any vibration in any gear, on med throttle, hard throttle, coasting etc at under 89km/hr.

Yet to push it past 95km/hr on throttle in-case it rattles to death!

Any help would be appreciated!

[trev]

Sounds like not the obvious seeing you have a new front shaft,presuming the balance is O.K. Have you considered an engine mount?Under throttle will load the mount differently to just coasting.
Have a look underneath and see how far above the metal base the rubber is.

Trev.

[choppo]

Thanks Trev. I'll check the engine mounts on the weekend.

Didn't mention before so as not to bias replies, but any thoughts on it being the Auto? I dropped it into 3rd, accelerated upto 95km/hr and I could swear the frequency of the vibration was higher.... But with the engine reving higher I'm open to that being an inaccurate observation. Could also swear I intermittently lost overdrive for a while too.
After 2 hrs of driving trying to work it out I was hearing and thinking all types things!

One other detail (maybe related to engine mount diagnosis), when I hit a speed hump I get a 'clink' from the front right.

Can you quickly explain engine mount diagnosis. Do they collapse or break? Try to lever engine and see what happens? You mention the gap in the rubber mount. What should it be?
Thanks in advance!

[schuy1]

Re engine mounts, Looking from underneath you will see 2 holes in the bottom of the mounting. looking into these holes you will see the rubber of the mount, there should be a space 'tween rubber and metal . If there is no space or you can not insert a rod at least 5-10mm in hole the mount is collapsed.
There is also a possibility of a cracked flexplate in the auto, they do crack. there is an inspection hole in bottom of bellhousing.
Cheers Scott

[bsperka]

Perhaps unrelated but the 'clink' from the front right may be steering ball joint. Helped diagnose this on another dosco recently.

[EvilGTV]

I'd be investigating the 4 main balljoints on the diff housing... If they're flogged out, you can get a change of wheel alignment when under power, and dependant on tyres that will induce a death wobble. Would also likely explain the clunk in the front end. You should be able to detect play in the top one by checking it just like a wheel bearing, bottom one not so easy.

If it's that bad though, I'd expect the top one to have easily discernible play, as dad complained of a shimmy (not as bad as you describe) in his D2 that came up whenever it felt the need, which he could stop for a while by giving the brakes a good tap. Inspection revealed quite a lot of play in the upper balljoint, think it equated to a couple of mm at the outer diameter of the tyre.

[choppo]

Thanks for all the replies guys. My garage consists of the bitumen out front on a 30deg slope! BUT Saturday week I'm moving to a place with a huge flat shed.
Time to get underneath with a jack and stands at the ready and give it a good once over. Will let you know!

[Franz]

D2a auto td5 '03. Have a weird vibration at 89km/hr. By weird i mean;

Only happens at 89km/hr + with throttle applied. Replaced front shaft with a Tom Woods to no avail.

What has me buggered is it has something to do with throttle input i.e. driving at 89km/hr all good. Accelerate to 95km/hr a high frequency vibration occurs. Like an out of balance wheel, but no feedback through steering. So back off to 89km/hr all good. Get to a decent decline and the car coasts to 100km/hr NO throttle.... NO vibration. If i place the slightest hint of throttle, and i mean the slightest hint of throttle, not even accelerating down the hill it vibrates again. Foot off throttle and coast at 100, no vibration. Touch throttle, vibration.


Additional info: doesn't have any vibration in any gear, on med throttle, hard throttle, coasting etc at under 89km/hr.

Yet to push it past 95km/hr on throttle in-case it rattles to death!

Any help would be appreciated!

Last time I had this problem it turned out to be a dropped weight on the rear propshaft. Inspect the shaft first and if you can't see anything obvious, remove the rear shaft and take it for a drive.