Subaru 4wd system.

Ok. When I hit c70mph over 3,000revs the front of the car suddenly starts to vibrate severly. Its getting worse, if I backed off it would stop however yesterday the vibration followed my speed down to 40mph. When I came to stop and started off again the vibration had disappeared.

Now I’ve redlined the car to see if it’s the revs in 2nd/3rd – the car pulls fine and no vibration at 6,000revs. The severe vibration only appears when Im on the motorway at 70/3k+.

Elimination:
-It cant be the suspension as the car would pull when I let go of the wheel (even on the motorway the car doesn’t pull/stays dead-straight). I have also visually inspected the suspension boots etc for leaks/splits.
-It cant be the wheel balancing as the vibration was still there when I reduced the speed on the motorway and I cant drive through the vibration?
-All tyres are inflated/no imperfections in sideways
-There are no leaks from the engine etc
-The car doesn’t overheat/rise above its normal temp, engine revs don’t rise/erratic etc, checked oil and coolant levels- fine.

(I could be wrong on the above- including balancing?). A Kwik Fit told me you can drive through the vibration if it is balancing?!

Could it be a dodgy engine mounting?- but this would vibrate the car at any speed inc when I redlined the car?
Loose Driveshaft? (as above?)
Something else lose in the engine bay (gearbox etc)- had a new clutch fitted a month ago.

I just want to eliminate/trouble-shoot as much as poss before I have to drop the car off at the indie to investigate. I'm not very flush at the moment.

 

Brakes discs out of balance, happened to me.
Sticking brake pads on one side. ????

 

Will check. It couldnt be the central diff? or...the universal joints on the driveshafts?? (GULP)

 

Buckled wheel? Flat spot on tyre/s?

 

Good point, will check for flatspots

 

A friend just mentioned it could be the transfer box? (A few months ago I had the clutch replaced)

 

I would also plumb for brake discs or the hubs. I have just had to have a new hub fitted with ball joint as the hub was out of whack and although the discs were fine, the wheel and disc just followed the line of the hub and bearing

 

How can you check if its a hub or disk problem?

 

Up on a ramp, spin the wheel by hand and watch the rotation

 

Up on a ramp start and run up to speed, a worn bearing is easily spotted, even if still quiet.

ECU reset needed after tho'.

HTH

dunx

 

check gearbox and diff mounts, as they can make your prob shaft out of balance.

 

Ok. Its returned. With a vengenance. Noticed a low vibration now at lower speeds and again as soon as I head 60ish on the motorway it starts:

a) Does it go (immediately) when i dip the clutch and coast?
- As soon as I dipped the clutch in it went/smooth as a babies bot. Even though I scrubbed no speed off at all. Did this a fair few times- immediate smoothness.
b) Does it go if I brake, lightly or firmly?
- No
c) Does it go immediately if I let right off the throttle? (no)
Revised- if I lift off the throttle it lessens considerably but returns asap as soon as I apply any throttle

Taking it the to the Subaru indie today (top lads)- if its up on a rmap would it be quick to diagnose???

Err does this mean the propshaft is knackered? Or can it (usually) just be reslotted? Expensive??

 

i have this exact same problem,am looking toward the prop shaft



only slight attempt at moving it but you get the idea.

will swap prop and see if it helps,mine is intermittent tho,1 day at 70 its fine,the next it vibrates like mad for 10 miles then just stops with nothing changing/speed etc

very weird

 

Ok, I should have posted back. Car up on a ramp the inner cv joint had flung a great amount of grease up and around. It also came apart as in bits as soon as we pulled the driveshaft out- thee cylinder housing of the joint is 'lipped' to prevent the bearings coming out yet they all did. Plus the outer cv joint- although the boot itself was in normal condition/no signs of deteriation when you articulated the joint it felt like a bag of broken glass. The previous owner probably though driving AT big kerbs was normal for a softroader. Idiot. Replaced with a secondhand driveshaft and hey presto. Fixed. Thanks to Adge speed.