Very strange vibration

benwarn · Post by **benwarn** » Mon Nov 17, 2008 8:53 pm

right, this one has me totally stumped!

When accelerating the whole car shakes, like all the wheels are really far out of balance (but they're not).

things to note

1. 2003 forester 2.5 manual
2. Only happens when the car is warm/been running for a while.
3. Only happens under acceleration, not just cruising along or deceleration.
4. Is speed and gear independent

Anyway, I'm Stumped! Any help would be VERY much appreciated

thanks in advance

bluesteel · Post by **bluesteel** » Mon Nov 17, 2008 10:55 pm

could be a busted engine mount and the engine is shaking under load/acceleration

or could be a cv on the way out and vibrating under acceleration

benwarn · Post by **benwarn** » Tue Nov 18, 2008 7:30 am

hmmm, yeh it's jsut so strange that it only does it once it's hot, but yeh, could be a mount, i'll have a look

brumbyrunner · Post by **brumbyrunner** » Tue Nov 18, 2008 10:19 am

could also be tailshaft. either unis or bent.

benwarn · Post by **benwarn** » Tue Nov 18, 2008 10:41 am

yeh it seams pretty straight, and do the unis heat up?

brumbyrunner · Post by **brumbyrunner** » Tue Nov 18, 2008 11:17 am

lol. The tailshaft can easily be bent enough to cause a vibration without visable damage. Unless the unis are completely flogged out, and it wont take long once they're worn, you might not be able to identify the problem without removing the tailshaft from the car. Same goes for driveshafts. Engine and gearbox mounts are easy so check them first.

YouTube · Post by **El_Freddo** » Tue Nov 18, 2008 11:21 am

brumbyrunner wrote:could also be tailshaft. either unis or bent.

That would have been my bet too, I'd be going for the uni's rather than bent...

Bennie

benwarn · Post by **benwarn** » Tue Nov 18, 2008 12:03 pm

sweet, thanks heaps for all your help, i'll let you know

AlpineRaven · Post by **AlpineRaven** » Tue Nov 18, 2008 4:06 pm

I would get CV joints checked first.. Happened to me once.
Cheers
AP

benwarn · Post by **benwarn** » Tue Nov 18, 2008 4:33 pm

yeh both front drive shafts have a very slight bend in them, tht hapened in my corolla once. i spose it could be that. Maybe i could take them both out and see if it stil does it?

benwarn · Post by **benwarn** » Tue Nov 18, 2008 4:34 pm

tho why when it heats up? maybe because they lengthen slightly?

Xtreme_RX · Post by **Xtreme_RX** » Tue Nov 18, 2008 6:22 pm

I think it will be your front drive shafts. I do recall there being an issue with some forester/liberty/impezza drive shafts getting strange vibrations.
A WRX Sti drive shaft was usually was the fix.......

benwarn · Post by **benwarn** » Wed Nov 19, 2008 7:09 am

the front drive shafts look SLIGHTLY bent, but i dont know if it's enough to cause such a vibration, i guess i could change them both, but it'd suck if it wasnt them! If i just take them out the box wont leak will it?

AlpineRaven · Post by **AlpineRaven** » Wed Nov 19, 2008 7:30 am

benwarn wrote:the front drive shafts look SLIGHTLY bent, but i dont know if it's enough to cause such a vibration, i guess i could change them both, but it'd suck if it wasnt them! If i just take them out the box wont leak will it?

Nah it won't leak, it might have small amount of seep but not much. Take the drive shafts to drive shaft specialist to get them checked out. Yeah if they are bent it wld cause vibrations because they're turning offset,
Cheers
AP

benwarn · Post by **benwarn** » Wed Nov 19, 2008 9:00 am

but why only when they're hot?

Post by **Alex** » Wed Nov 19, 2008 12:10 pm

mate, to be honest, theres nothing on the car that will make a vibration once it warms up. (unless you have major engine or gbox problems)

1. check the stupid stuff first, such as the WHEEL NUTS and CASTLE NUTS(hold the cv shaft to the hub)
2. otherwise i'll put money on cv shafts. Ive recently fixed a liberty with this exact problem, it had a pretty badly worn front inner joint.

all the best.

alex

benwarn · Post by **benwarn** » Wed Nov 19, 2008 12:12 pm

cool, i'm taking it into a driveshaft place to have it looked at, but honestly, it only happens after about 5 mins of driving, which is why it's so weird

L-Raiser · Post by **L-Raiser** » Wed Nov 19, 2008 2:05 pm

Just an idea, but would the temperature of the oil/grease in the CV's be a factor...? When COLD, they have a thicker viscosity, then when hot, gets looser, more slippery, then....WOBBLE WOBBLE bang...?

benwarn · Post by **benwarn** » Wed Nov 19, 2008 5:45 pm

ok the verdict is:

because it's lifted a little bit the front inner universal joint is a little too tight and angle.

the local driveshaft fella is going to machine it down a bit so there's less restriction on movement, and he's going to make up some spacers to drop the box slightly, he sound like he know what he's on about.

AlpineRaven · Post by **AlpineRaven** » Wed Nov 19, 2008 5:56 pm

benwarn wrote:ok the verdict is:

because it's lifted a little bit the front inner universal joint is a little too tight and angle.

the local driveshaft fella is going to machine it down a bit so there's less restriction on movement, and he's going to make up some spacers to drop the box slightly, he sound like he know what he's on about.

Ahhhh....
Cheers
AP