Bad clunk/thud from rear of car?????

[lukevincent]

I keep getting this awfull clunk/thud sound coming from the back on my 98 VT series 1 s'pac.

I have no idea what it is at all.. and ive recently had a new diff put in so i know for sure its nothing to do with that.. Ive had the sound before and after the installation of the new diff also..

I get this sound when slowing down fairly quickly when it drops from 2nd to 1st, i also get it when changing back from second to first just cruzing at say 25-30kmph, i get it when accelerating around corners in 1st and mainly second, and giving it some pedal in 3rd and dropping back into 2nd or high revs in second and accelerating then.

I have yet to hear the thud in 3rd to 4th gear 70/80km+, if there is its hardly anything in comparison

Also.. can get the same sound SOMETIMES.. hardly ever but.. from bumps on the road.. (big ones) and if the handbreak is applied at whatever speed, weather it makes me come to a stop or not.. at 5kmph you still get a massive THUD no matter what.. which to me is not normal at all.

any help would be awsome, and to add, i have already put in one of those nolathane diff mount inserts but still no difference.

hope someone can help

[Rhin0o8]

How is your TailShaft ?

[lukevincent]

No idea havent bothered looking at it... lol.. when i did the diff it seemed nice a tight but then again... to mention it i do get a bit of backlash through changing through Park->reverse->Drive.. etc at times.

but ive been set on that its something suspention wise.. ? getting a pedders check on wednesday so will see what they say...

Ive had it up on the hoist and everything seems tight.. CVs are good.. left has a tiny incy bit of play but nothing at all to worry about.. everythings prety well good and tight from what i can see... i know that my crossmember bushings need replacing but can they realy be the source of these sounds?

[jazza15]

Your centre diff mount bush may be torn. Just get one that isn't torn from the wreckers and/or get a diff mount insert to fill the void.
If it is coming from the left or right, then it will be the outer mounts. My rear left was pretty much torn right through though and I didn't have any noise that I can remember...
Back on the diff mount: it is a rubber and metal bushing. I was talking to a guy at Pedders who has seen a few cars that had it go, where they had checked everything and it turned out to be that bush torn, when you think about it though, it makes sense

[lukevincent]

I have an insert in it already but and no improvement

[jazza15]

Yea sorry, didn't read the whole initial post in detail as I was straight away sure of what it was haha.
So basically there are those 3 mounting points where a thud at low speed would be evident for a sudden shift of momentum.
If there are no noises from the wheel bearing, then that rules out that.
The rear tailshaft yoke is the metal one in your car? the one from the gearbox is rubber though, like in the vx onwards (at least it is in my car, with the metal at the back). As you may have heard, they have been known to tear, and with a supercharged 6 in front of them, it would be no wonder.
Other than that, I am fresh out of suggestions, but do make sure that you have completely ruled out that centre mount being torn anyway, as I was strongly thinking that it would be the culprit, despite not reading that you had already fitted the insert

[lukevincent]

yeah cheers mate, i guess i'll overlook my tailshaft again hey and see weather there is something there thats the weak link.

wheel bearings are definatly goooood, and yep installed the diff mount insert.
and also yeah being a series 1 VT have the metal back and rubber front.
cheers for that mate, will look into those couple things.
im still stronly leaning towards that its a suspention issue because the thud is only heard when greater loads are put on the back end.
maby my shockies are shot? or the top mount bushings on them.. .. hahah hows that for thinking.. im gana go look now hahah..


second thoughts i'll wait for my pedders report lol

[Rhin0o8]

Does the VT have a Uni Joint in the Drive line .. im guessing, and only guessing its between the trans and tailshaft ???

Pedders still do a $14 28 point check these days?

[lukevincent]

yeah i'll check my tailshaft/drive line over the weekend and yeah pedders still do the $14 check up which i have booked wednesday coming so will see then.

will post any updates

[mike_is_bored316]

Join the club i got a bad CLUNK! aswell, Pedders still does the $14 28 point check and if they dont i know that dunlop service centres do a safety check for FREE apparently

[lukevincent]

Yeah sooo anoying haveing a bad clunk hey, especialy from the rear of the car lol. sooooooo many things that can be wrong.

Have you tried narrowing down the problem?

[Rhin0o8]

any update on this problem?

found a solution and/or fixed it?

[CommodoreAdict]

seconded??

[VTSL67]

i had the same problem. i looked over the tail shaft 1000's of time. it turn out to be the link pin bushes were flogged, just cause the rear sway bar (i think thats wat its called) to move. replaced em and noise was gone.