Knocking/Clunking between rear wheels, under load?

[neil2849]

Evening all, just driven back from work tonight, and noticed a clunking noise, its in time with the wheel's rotation, and coming from the rear, possibly near side of the car more so than directly in the middle but that could be because of where im sitting, i thought at first it might have been debris (9 inch nail from driving past the tip etc!) in the tyre, but having checked, there's not a mark on the tread or anywhere else for that matter, so im sure its not. Unless its to do with the caliper, but that seems in good nick, plus its happening in gear only.

The noise appears at about 2200 rpm in first - fifth, but is most noticeable in second (probably because of the engine noise drowning it out) Weirdly however it doesnt appear when im not in gear, nor when the road condition is poor?!

Ps. its a manual and its a 1989 F reg. 944 - non-turbo. Ive had a brief scan about online etc and i seem to get everything from CV joints to torque tubes and suspension bushing, but none of the descriptions sound exactly right... if it was CV it would happen from lock to lock presumably, and it doesn't, and with torque tubes and bushings it would happen when im in neutral too??lol Its driving me crazy, and im already seeing the pound signs roll down!lol []

Any help would be much appreciated! Thanks guys & gals!

Dan []

 

[sulzeruk]

Possibly a CV starting to go or the final drive in the gearbox if the noise increases with road speed. If it is engine speed related, could be torque tube bearings, clutch relaease bearing, etc.
Alasdair

 

[ChasR]

If I were you I'd just check over the brakes (and handbrake first).

The CV tests will not work on a 944 since it's RWD and that test is for FWD where the outer CVs need to work at much more extreme angles. I reckon it's the CV joints with it possibly being the gearbox (Low oil level? I'd change the oil anyway on the basis that it's probably never been changed anyway). Regarding the CVs, does the car take up slack when you drive off? Get under the car and give the driveshafts a wriggle in order to check for play.

 

[zcacogp]

I'd suggest it could be CV's as well (the CV test DOES work on RWD cars, but not as well as FWD cars. When under hard lock, the outer axle will work harder than the inner one and be noisier.)

It's worth looking at the brake calipers more closely, and particularly the cruciform clip that holds the pads in. When the pads wear, they move to a looser part of the clip and can become loose. This can produce very similar effects to that of a worn CV joint. If the pads aren't held in place tightly by the clip, that's probably the explanation. It's cured by taking the clip off and bending it slightly. (Easier said than done, but an easy DIY job if you have strong fingers and some patience.)

If it's not brakes then wiggle the driveshafts, as Chas suggested. If in doubt, take them off and take the joints apart and check for signs of wear on the drive faces (easily seen.) Swapping the drive shafts from one side to the other (easy job - they are equal length) will swap the drive faces over. (If anyone wants to disagree with this then think about it for a while ... )

Changing the gearbox oil is always a good thing.


Oli.

 

[edh]

CV will still knock when cornering if it's shot - well worth checking for play in the shafts.

You really need to pin down whether this is related to road speed or engine speed

First thing I'd do though, is check all your wheel nuts....

 

[chrisg]

Just to throw in my thoughts, it could well be a brake pad rattling/ rotating then dropping.

I picked my car (951) up on Sunday and had a very similar road speed related clunk, that disappeared on application of the brake.

When up in the air in gear and the wheels rotating, tickover and 2nd gear, you could actually see the outer rear o/s pad being 'picked' up by the disc(slight wharpage) then dropped. The stainless steel cruciform clip/ cloverleaf wasn't pushing the pad in far enough to hold it tightly.

Easy fix with bending of the clip and use of a spring washer

 

[supersport]

ORIGINAL: edh


First thing I'd do though, is check all your wheel nuts....

I would second that having had a car with loose wheel nuts and had somone spend ours trying to work it out only to eventually check them to find them loose. It happened a couple of days after having new tyres put on and about 300 miles.

Sounded like a knocking noise.

 

[dirtydirtyharry]

LOL, this is a coincidence but my 944 is in the garage today with EXACTLY the same problem. I get a loud knocking noise in time with the wheel revolutions. it sounds like it is from the rear passenger wheel. It only happens when I apply the gas however, ie while car is coasting it doesnt happen. I was told on here that it sounds like the cv joint so took it to the garage for an inspection today. Typically on the three road tests the sound wasnt happening []. They said that the brakes needed a clean up and reassembling and that the rear passenger cv joint did have 'slight' wear but nothing of worry.

They said that they will gladly put a new cv joint on if I can source one. Apparently they are not easy to get hold of these days.

I know fine well that the noise will start up again when i drive home tonight. Its just so loud that it annoys the hell out of me and is a bit embarrassing. [:'(]

 

[edh]

Berlyn look to have all the CV's or driveshafts you might need. I'd be a bit suprised if you couldn't get them. (Although I know turbo clutches were completely unavailable in the UK at some points last year)

 

[neil2849]

right ok, so... thanks for all the help guy's ive been abit snowed under so haven't been able to get an update on here but...
The noise does not happen when im in neutral, so im pretty sure its not wheel related although ive just bought a rear wheel bearing which im having fitted some time in the next few days. Basic thinking was do the cheapest things first...£50 quid for a shiny new bearing...

Anyway so in response - Dirty Dirty Harry - i totally sympathise - it drives you insane!! Even worse as you say it actually goes away, sometimes fof days at a time, then out of the blue, no warning it just comes back! IMO i think its either the torque tube bearings or the clutch rubber - but for it to be so specifically over the rear passenger wheel im taking the advice of my mechanic friend and going for the wheel bearing. ps. he also noted wear on the diff, but an appropriate amount given the age of the car and seems to hold up to inspection!

Again IMO i dont think its the CV because noise is not in any way affected by turning left to right, and in fact its worse when shifting up and down in a straight line. I can drive on the motorway and it will dissappear then re-appear when i come off the slip road - obviously im trying not to use it much, but i hate to say it, an i know it sucks, but im thinking if i just keep an eye on it, and continue as normal IRO maintenance etc, ill find it as soon as it goes!

On another point - i drove back from work the other day and found a stray snapped belt hung over the axle of the front passenger side... i immediately thought the two must be related until i looked in the engine bay and couldnt see one thing missing! I even parked next to my Dad's and we did a quick side by side comparison, there's no where for it to have come from! I know what your thinking, ive just picked a stray belt up off the road... Nope, was definately a porsche belt, it was stamped and everything, only we again dropped the car round to a mate who confirmed it hasnt come from anywhere, most likely to have snapped years ago, been replaced and subsequently half of it was left by the guy who did the replacement who thought it had cleared!

DRIVING ME CRAZY!!!lol

Anyway, while the weathers dry and ive repainted the sill's im taking the oppurtunity to jack the car up and see if theres alot, if any, play in the rear wheel + give the calipers a good looking at. Although ive already almost dismissed these as the cause due to the lack of noise when in neutral.

Thanks again all for the help, i'll update in due course!!! [] LOL

 

[DivineE]

Does the gearbox whine at all? Take the carpet out and go for a drive. My diff on my first lux clattered a bit when I bought it and then failed but it had a noticeable whine.

It could just be the exhaust mounting in front of the gearbox which often gets dislodged and can catch on the gear linkage but if you say it sounds in time with the rotation of the wheels and is in the middle of the car at the rear it sounds like gearbox to me. Mine was not as expensive to replace as you might think. Very cheap actually about £100 and 4 hours labour. 2 off 2 on.