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Pinion Bearing Questions

Ca. 500 miles or so ago, I started hearing a low-level whining noise whenever my foot was on the accelerator. I took my car in for 105K mile maintenance, and asked that the noise be checked. The mechanic told me that the pinion bearing would need replacement, but not immediately (estimated cost: $1700). He informed me that the noise would get louder over time, and that I would know when it needed to be replaced; also that I would not be doing any other damage to my car by waiting so I could save up a bit before I have the work done. My questions, as a person who doesn’t know much about cars but would like to learn… Is it truly okay to wait? How will I know when it is time to have it replaced (just that it will be very loud)? How common is this kind of problem, esp. at my mileage (105K)? Does $1700 sound like a fair price? (I’ve had all maintenance and work done at a dealer, feel pretty comfortable with them, but am pretty ignorant when it comes to this stuff.) Thanks in advance.

Is this Outback an all wheel drive vehicle? Is the whine coming from the front or back?
Does this have a manual or automatic transaxle?

A whine under acceleration usually indicates an incorrect mesh of a hypoid gear set. A pinion bearing failing gives a roaring sound under acceleration. It is possible that the bad bearing is allowing the pinion to move and change the mesh of the hypoid gear set.

You might get a second opinion from an independent transmission shop.

Thanks for your response. It is AWD, automatic. It sounds to me as though it’s coming from the front.

You need to stop driving the car immediately and check the final drive oil level. There are two main reasons why the oil level can be low.
One is an internal seal leak that cause fluid loss into the auto trans fluid over time. This usually occurs gradually and the driver may become acclimated to a whine until the moment the transaxle blows up.
Note in this pic where the dipstick is at. (the yellow part on the PASSENGER side of the transaxle)

The other is the tendency for some lube techs to get in a hurry and remove the final drive oil drain plug by mistaking it for the engine oil drain plug. This is not a rare thing to happen and also causes catastrophic transaxle failure. Think hard about whether this problem seemed to surface after an oil change.

Hope that helps and in case you’re wondering why I refer to it as a transaxle that’s the proper terminology rather than the word transmission. (nitpicking over semantics I guess)

Thanks for the additional information. I should have mentioned – while the car was in, I had all fluids checked, oil changed, multi-point inspection and the timing belt replaced. All fluid levels were fine. The whine began about 1,500 miles after the previous oil change.

The car should still not be driven until it is verified that the final drive (part of the transaxle/transmission) oil level is what it should be.
It’s very easy for someone to check the transmission fluid with one stick and just flat overlook the stick or plug for the final drive oil on the other side.

These things start out as a faint whine which then becomes a louder whine and eventually this can become a loud bang; followed by coasting to the side of the road with a transmission that is not repairable due to the extent of the damage.

I worked for several Subaru dealers and have been in the middle of more than one of these destroyed transaxle situations. The majority were caused by quick lube facilities and the others due to DIYers.

If the pinion bearing disintegrates you are looking at a more expensive repair. replace it sooner than later is my advice,

Subies can be very $$$ to repair when bad. Would check with a good local mechanic that knows them well. Had a bearing go in the rear diff. ended up junking it as it was too old to fix-per my mechanics advice after I put his kids thru college!

Hopefully the OP will not proceed with this repair on an allegedly defective pinion bearing because the end result will probably be a bunch of money with no improvement.

To even access that bearing, which is not the cause of this problem, will require the removal of the transmission/transaxle/whatever you want to call it and a complete diassembly. This would mean a complete transaxle overhaul.