Hi Guys
New to the forum and I hope you can help
I have a Jan 05 WRX with rear diff problems (42K)
The car developed a grind from the rear diff. We had the car up on a two post ramp and listened with a stethoscope and the rear diff pinion bearings were clearly the problem. No other noises elsewhere. Got a second opinion from a Subaru garage and they came up with the same conclusion
Next step was to fit a second hand diff. This came off a car of the same model, age and similar mileage
---- and similar grinding noise, but not as bad.
I assumed that we had got the analysis wrong and decided to let the noise get worse so we could be very sure of the problem (plus no easy access to the ramp at that time)
The noise has got worse and we checked again and the grind is the pinion bearings in the second diff
The original diff is now off for a re-build and the car is still running with the second hand diff in place
Subaru dealers and mechanics say that pinion bearing failure is unusual
Is this a problem others have had??????
A friend who is a very experienced mechanic on racing off road vehicles said this could be a batch manufacturing problem. He has known of manufacturing batch faults that have occured on Land Rover gearboxes

 

Hi mate,

Can I just ask where you sent the diff for a rebuild?

Cheers,
Matt

 

To have a pinion bearing failure on a Subaru is almost unheard of. To have two diffs doing the same thing in the same car is almost certainly wrong diagnosis.

We have found in the past that A diff noise is caused by someone jacking the car up clumsily at the rear end. Either side, there are two locations for the front X member of the rear axle, close by the jacking point. The mounting is held in place by a shaped piece of steel and jacking up on it bends the steel and you get metal to metal contact where it should be absorbed by a rubber mount.

This bent steel plate causes a grinding noise..................

Check it out - David APi

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David

Thanks for the reply about the sub frame mountings as a possible cause of the noise. The whole sub frame and rear diff mounts have been checked and none of the mounts are damaged or in any direct metal to metal contact with the body, all is in order including the rubber harmonic weights

We have tried to resolve this diff noise for 5 months and so far I have 3 further other opinions (all very credible people) over my own investigations, all considering the pinion bearings as the most likely case. As you say no one has experience of pinion bearing problems in the past. This is why we have looked very hard to ensure we are not putting this down to the wrong diagnosis.

I have found some reference to this problem on a forum in the USA, but there seems to be no clear cause established.

The above is why a manufacturing batch with a potential quality problem as a possible cause

All we can do is rebuild the first diff and hope this sorts the problem. The noise is getting worse so we should be able to get this resolved

As you can image this is becoming very irritating and expensive

The car was involved in a front end accident about 3 months before this problem started and again we have extensively checked to establish if any residual damage to drive train may be the cause

If you drive the car you initially think this is a rear wheel bearing but a listen with the stethoscope at all 4 wheel bearings establishes no noise. This applies to the centre and front diff bearings as well. The rear pinion bearings are clearly noisy via the stethoscope. This noise is the same if the car is on and off load and coasting in neutral.

 

jamesanderson1

I have an e-mail notification that you have posted a reply but it is not coming up on the thread

 

Rabbitaway,

I initially thought mine was a rear wheel bearing as the sound matched but once the car was jacked up the sound was clearly coming from the rear diff. I'm going to take it to another Subaru dealer in the next few weeks for them to have a look.

I only noticed it when I was rolling in neutral down a big hill at about 65mph with the stereo off and could hear the sound in the cabin. I have had it for about two months now and it hasn't got any worse.

Cheers,
Matt

 

So don't roll down hills in neutral with the stereo off

Diff problem cured, now wasn't that easy?

 

Did you ever find out the problem. Mine does it loud at 65mph and light throttle

 

what the hell were you doing coasting down a hill in neutral anyway?

 

Saving petrol but not using engine braking...?

 

I hope it wasn't an effort to save petrol as you actually use more idling in neutral than you would on the over-run in gear off-throttle down a hill.