2007 Impreza - knocking sound in the back

[mkinraj]

Hi Subaru gurus,

 

A question for you. My 2007 Impreza, SW, 115 k miles, manual transmission, developed a knocking sound coming from the left rear end of the vehicle. It happens especially when turning left and accelerating at the same time (on lower gears) and goes mostly away after driving 2-3 miles. Immediately after start, it even happens when accelerating (without turning). Turnig by itself (without acceleration) does not iniciate the sound. Originally, my feeling was the nocking is from the inside, so I checked things lik the spare, jack etc., even tried to squeeze a piece of sponge to the back gate to prevent it from possible vibration, but no result. So, any ideas? Rear axle? Suspension? Bearing? Would apreciate ideas.

 

Thanks, Michael

[TKFlight]

Could be rear axles, bearing would be a grinding sound. I would even check the bushings they are known to make strange sounds.
 

[1 Lucky Texan]

accelerating causes 'squat' so, all the rear suspension gets compressed. 'Knock' doesn't 'seem' like a bearing. though, soob bearings DO exhibit odd/varied symptoms sometimes when failing, knock doesn't seem to be one from what I have read.

 

suspension parts or possibly diff bushings i guess ??? also, definitely worth checking lug nuts/studs, rear axle nuts and brake shields, etc.

[forester2002s]

Brakes?

Try gentle brake application while the knock is present. Does it change the sound?

Try the same with the parking brake.

[JasonInMontana]

Hi Subaru gurus,

 

A question for you. My 2007 Impreza, SW, 115 k miles, manual transmission, developed a knocking sound coming from the left rear end of the vehicle. It happens especially when turning left and accelerating at the same time (on lower gears) and goes mostly away after driving 2-3 miles. Immediately after start, it even happens when accelerating (without turning). Turnig by itself (without acceleration) does not iniciate the sound. Originally, my feeling was the nocking is from the inside, so I checked things lik the spare, jack etc., even tried to squeeze a piece of sponge to the back gate to prevent it from possible vibration, but no result. So, any ideas? Rear axle? Suspension? Bearing? Would apreciate ideas.

 

Thanks, Michael

Michael,

 

My Subie had a knocking sound that sounds much like what you are describing. It turned out to be bad struts in the rear. the knocking sound occurs as the shafts shift around inside the cylinders.

[idosubaru]

Tricky one.  I think previous comment about strut is a good place to start.

Grab it and shake it or pry against it - if uncertain compare it to the other side.

Look for a leaking cylinder - wetness around the strut rod seal.

The free test if they're interchangeable would be to swap struts - left to right and right to left - and see if the sound moves with it.  But that's labor/time.

 

Front axles routinely make sound under load/while turning.  So at first it smells of axle issues.

But there's two clear suggestions it's not the axle - Subaru rear axle failure is nearly unheard of - most 1980's Subaru rear axles are still fine....minus boots aging. 
And you can tell which side it's on - the axle would be harder to delineate which side...you'd be uncertain i would think which side it's on.

[idosubaru]

Michael,

 

My Subie had a knocking sound that sounds much like what you are describing. It turned out to be bad struts in the rear. the knocking sound occurs as the shafts shift around inside the cylinders.

 

thanks for posting, that sounds nearly the same.  what year/model subaru was that out of?