Help - Strange clunking/clacking - I'm stumped

Dedman

Dedman

Forum Member
Joined
Dec 3, 2012
Messages
766
Location
Perth Western Australia
Car Year
1999
Car Model
Forester
Transmission
5MT
My car has had a strange sort of mechanical clunking for a while now. It shakes the car and is related to rotation. I first noticed it when climbing very steep hills as slow as possible. It seemed to very very strongly correlate with the high load (steep climb) and front suspension with less than normal weight on it (suspension more drooped than usual).

During every day driving it never occurred, off-road it never occurred (except for steep high traction climbs), accelerating as hard as I could it never occurred, turning on a sealed road with the DCCD locked it never occurred.

This weekend I was doing some pretty hard core driving and after bottoming out in a rut it suddenly got exponentially worse (it could be a new fault but it sounds exactly the same as before so I think it is the same). It now makes the noise on climbs, when starting off from a standstill.
My initial thought was that it was my front CVs giving out however I have now changed them and it still does it.
The below video shows the noise quite well and the second half shows when it first started (at the end of the attempt at getting over the climb)

[ame]www.youtube.com/watch?v=lNcEldVb5AY[/ame]

The now that the problem has got worse it seems to start when under high load and then is occurring constantly until faster speed is reached, however after it stops dropping speed back down does not cause it to restart...
Going down the freeway the car acts normally, no noise no vibration. On road it only occurs at really slow speeds (1st gear under 1500rpm) and is especially bad if you lock the dccd and make a turn on a sealed road (again only slow speed).

I am currently thinking it is something to do with the tailshaft however I have checked all the unis and the seem free and not loose. The shaft can move around in the mounting in the middle of the shaft a bit but I am not sure how normal or otherwise that is. The mount looks fine but it does not take that much force to move it up and down 10mm each way.
I am wondering if maybe I have bent the tailshaft somehow but given how tucked away it is I feel it is not that likely, especially considering the exhaust in not in that bad a shape.

Any ideas or comments would be much appreciated.
 
^ The Haynes manual seems to suggest that there should be zero clearance in the rear propeller shaft bearing.

I also seem to recall that this bearing was very snug on my '93 Impreza. I haven't ever looked at it on either of our Foresters, but would like expect it to have no radial play at all. After all, its sole reason for existence is to stabilise that shaft, same as on a Mack truck ... :iconwink: :lol:.
 
Possibly steering... had a similar issue with a gen 3 outback but would happen onroad. Turned out to be the right side inner tie end rod had play and no grease. Never had anything like ir before.
Also when were your ball joints last done?
 
I'll have a look at my centre bearing tomorrow but that's my guess. Sounded a bit like El Freddos thumping in Ruby Scoo. His centre bearing was totally shot!
 
Now I think about it the centre bearing makes a lot of sense. It doesn't rattle or anything though just moves in the rubber mount without that much force. The stupid service manual just says check for abnormal movement which is not that helpful... Would be great if you could check NachaLuva :-)

I have also just replaced ball joints, tie rods and rod ends so it is unlikely that is that.
 
Just checked, there is some movement in mine, maybe 5mm each way. But its not what I would call loose or sloppy, it doesnt move easily
 
yeah I think some movement is normal as the centre bearing is surrounded by rubber - there's meant to be movement in the rubber so it acts similar to a suspension bush. You don't want a spinning bearing connected directly to your floorpan with metal. Does sound like maybe Dedman's may be flogging around excessively in there.

Would be good to get a go-pro or something stuck up there to video the bearing in action!
Also have a good look underneath for anything that might have bent into the path of something that spins - maybe an exhaust heat shield or something scraping on the tailshaft uni joints, something like that.

Would have to be something like this if the noise has a direct correlation to wheel revolutions as you've mentioned. Steering, balljoints etc seem unlikely to me for this reason.

It also could be something to do with the DCCD. The noise sounds a little similar to when the drop gears in my centre diff disintegrated themselves one time. I was running a 5spd turbo gearbox and had converted it to RWD only - the stock centre diff had been welded. The drop gears just smashed themselves to pieces after a while. I replaced them an changed to an actual mini-spool specifically for RWD conversions after that. But yeah, it made a noise similar to that not long before it went BANG and it wouldn't drive anymore.
 
I used to have a similar sound at slow speed, turned out to be the gearbox mount needed replacing.
 
Gidday DM

Just checked my SG.

There is around ±2.5-3.5 mm movement, but it doesn't move freely. It's not hard to move, but it doesn't want to, if you get my drift. The rubber mount holds it pretty central with some stiffness apparent when I try to move it in either direction. The rubber bush locates it a bit like an engine mount, but nowhere near as rigidly.
 
I forgot to add the noise in its less severe state occurred before and after a change of gearbox, rear diff, one rear axle, engine, starter motor, front axles, front wheel bearings, gearbox mount, gear selector bushes, tie rods, rod ends, ball joint, road and mud tyres and new struts front and rear.... Hmmm now I put it in a list like that it sounds like I should have just bought a new car haha.

Not sure about the centre bearing still, it very hard to compare between different people putting different amounts of force on it... Mine moves but takes a bit of force to do so.

Here is a pic in resting position.
15794499210_efb9600f8a_z.jpg

Pulling down
15981780155_0b9d02373a_z.jpg

Pushing up
15359515894_69cda68abe_z.jpg


I would say I would be putting 10kg force on it at a guess but it is very hard to estimate in an awkward position lying upside down.
 
^ I'd say that's knackered, DM.

Mine moves much less than half that far. Looks to me as if the suspension ligament is rooted ... :(.
 
Mine's similar to taza's, it's got more movement than that and makes no noise.

Stick the go pro under the car and go for a drive.
 
I don't know why I had never thought of that before idw! In this age of modern technology that is the perfect idea. Sure enough when I put the camera under there that centre bearing goes spastic as certain speeds. Not sure how you and Taza had more movement and dont have issues.... Maybe you don't drive slow enough...

Second half of video is at 15% speed
[ame]www.youtube.com/watch?v=4KzvpLe8doc&list=UU_uIq1hkQuQUavV1ovSLQhw[/ame]

NachaLuva, that is my plan, grab one from the wrecker on the weekend. Looking at the Jollys pricing I cant for the life of me work out how much that bearing would cost unless it is just included in the tailshaft price...

Thanks for all the assistance everyone
 
I think you have to get the tailshaft, not sure but I dont think you can get the bearing seperately.

Jollies is $46
 
AndrewT said:
Would be good to get a go-pro or something stuck up there to video the bearing in action!
Click to expand...

Hey I said it first lol :)

Awesome the things we have at put disposal to help now hey, good score, glad that's all it was! Should be a cheap and quick fix now :)
 
Hmm, might stick my camera under there and go for a drive. It doesn't make any noises but it's got some play so maybe its on the way out.
 
Why yes you did AndrewT you did. Sometimes I miss things when viewing forum on my phone.
I would be interested in what you find idw. You have to go slow though and apply some resistance with the brakes to get best results.
 
This is of interest to me as I just paid a fair bit for brand new uni joints and whole new rear section of my tailshaft - only bit kept was the centre bearing as the guy rekoned it was fine. Damn well better be!
 
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