Whirring noise between 50kmph - 60kmph (31mph - 37mph) | 92' Legacy Wagon (BF5) turbo

[Hersheythewagon]

Hi guys,

I bought a 1992 Legacy BF5 (wagon) turbo a couple of weeks ago, and the seller mentioned that the car had been sitting in one place for about 6 months or more before I got it. I did the usual engine, gear and diff oil changes along with some other minor repairs. 

The undercarriage and the engine bay was completely cleaned out with a Kerosene and Petrol spray gun as well.

A few weeks later, I started noticing a whirring noise that comes after I hit the said speeds and goes away or get's masked by the tire noise after about 60kmph or 37mph. The axels were replaced by the local mechanic that specializes in Subaru's here and is known to be good but the noise was still there.

The mechanic I mentioned, said that the noise could be from the center drive shaft or the out put bearing on the gearbox and the either of those parts will have to replaced as the noise seems to be coming right under the gearbox or towards the front left.

Would anyone know what the exact issue is or has faced a similar problem with their cars?

Thanks!

[doublechaz]

If it were mine, I would get a helper in the car and put it up on the frame lift.  Then while the helper "drives" the car at the stated speed use the mechanic stethescope to listen to the trans tailhousing and the mid propeller shaft carrier bearing and see which one is making noise.  It should be the carrier unless the car has always been driven by a meth'ed out gorilla for the last 50k.  You can use the same technique to listen to the front and rear diff, the wheel bearings and anything else you can think of.  Keeping in mind not to tear off any body parts by getting them caught in any moving parts.

Edited September 29 by doublechaz

[arse_sidewards]

x2 on try running it on stands.

Use the 1-2-3 selector to manually cycle up through the gears otherwise it will run right up into 4th in no time flat and you won't be able to run it steady state at 30ish.

My money is on wheel bearing.

[doublechaz]

Good point on the selector.  Mine is manual so I didn't think of it.

[Hersheythewagon]

On 9/30/2024 at 10:15 PM, arse_sidewards said:

x2 on try running it on stands.

Use the 1-2-3 selector to manually cycle up through the gears otherwise it will run right up into 4th in no time flat and you won't be able to run it steady state at 30ish.

My money is on wheel bearing.

Thanks! Mine is actually a manual transmission and not Auto. 

[Hersheythewagon]

On 9/30/2024 at 7:27 AM, doublechaz said:

If it were mine, I would get a helper in the car and put it up on the frame lift.  Then while the helper "drives" the car at the stated speed use the mechanic stethescope to listen to the trans tailhousing and the mid propeller shaft carrier bearing and see which one is making noise.  It should be the carrier unless the car has always been driven by a meth'ed out gorilla for the last 50k.  You can use the same technique to listen to the front and rear diff, the wheel bearings and anything else you can think of.  Keeping in mind not to tear off any body parts by getting them caught in any moving parts.

Thanks. That's a a great suggestion. 

[Hersheythewagon]

On 9/30/2024 at 7:27 AM, doublechaz said:

If it were mine, I would get a helper in the car and put it up on the frame lift.  Then while the helper "drives" the car at the stated speed use the mechanic stethescope to listen to the trans tailhousing and the mid propeller shaft carrier bearing and see which one is making noise.  It should be the carrier unless the car has always been driven by a meth'ed out gorilla for the last 50k.  You can use the same technique to listen to the front and rear diff, the wheel bearings and anything else you can think of.  Keeping in mind not to tear off any body parts by getting them caught in any moving parts.

To add to what I've said. While driving when I disengage the clutch while the noise is happening it keeps going till the speed drops below 50kmph, this means that the issue is not with the tranny right? I could be wrong but just thinking in a practical sense..

[doublechaz]

With a manual trans, rolling down the road at speed with the clutch in, the internals of the trans are all still spinning.  If you were rolling down the road at speed with the gear selector in neutral and the clutch in the input shaft would come to a stop, but the output shaft, center diff, and front diff would all still be spinning.  Compare to parked with the gear select in neutral and the clutch in all trans parts would be stopped except the throw out bearing at the clutch.  Parked in neutral with the cluth out would stop the throw out, but spin the input shaft.