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While driving at 80-90-100 km/h on the 3rd gear a strange noise starts from the rear, I guess it is from the diff or something... I checked the rear diff: no oil leakage. The noise stops if I slow down below 80 km/h or if I start driving faster than 100 km/h. What migth be the problem? Worn diff? Broken part in the diff? Axle?
What is a "universal joint"? (New to Subaru and to the forum!!)
Thanks in advance...
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'97 Legacy 2.5 GX Sedan AWD A/T

What kind of noise is it? A humm? A clunk? A clicking? A grind? A whine? A buzz? A thrid grade wind ensamble? Our rear diffs do hum a bit, and I have only heard of one person blowing one... I may be wrong though. The carrier bearing on the driveshaft makes a hissing sort of hum when it goes, and its not an uncommon thing. Let us know.

Cheers

An example of a universal joint is a the joint between the driveshaft and rear differential. The joint allows a variance in axial rotation between the shaft and differential due to mounting angle and drivetrain movement.

Steve

It's like a hummm. Thanks

Does it change in volume/intensity when you turn right or left? If it does, it might be a wheel bearing. Does the noise constantly change with vehicle speed? I know it is a bit dangerous, but jack up and securly support the car off all 4 wheels, and put it in a high gear and let her rip. Pay attention to the rear wheels, does one spin more freely than the other? Can you pinpoint the source of the noise (by using a short length of garden hose to your ear) while its jacked up and running in gear? If one wheel isnt spinning, but the opposite one is, block the opposing wheel so the stiff one spins and then listen for noises.

Did you check the fluid level in your rear diff? Regardless of its level, I would drain whats in it and refill it with fresh lube to the correct level (oil is a whole lot cheaper than parts). Even though it may show no signs of leakage, gear lube does evaporate (believe it or not) when its heated up, so some escapes from the vent... If it hasnt been changed in a while, the level may be lower than it should be. The diff will also make noise if the level is too high (they are pretty fussy about levles). See if you can find the source of the noise and let us know.

Cheers

Morgan (AKA the worst speller ever)

It does not change with the vehicle speed or with the turns. It just starts at 80 km/h, stops at 100 km/h. The level of the sound stays stable between 80 and 100 km/h.
Ok, I will try to check the fluid level at the garage tomorrow and I will write the result.
Thanks

I have checked the oil level, it was ok. I drained and changed it. The noise continues. But I've realized something else: if I drive the car on "3" instead of "D", there is no sound. Then, might it be from automatic gearbox?