'99 Legacy GT wagon "body boom"

[mwatt]

Any of you folks ever seen a REAR driveshaft or universal joint failure? In my '99 Legacy GT wagon (auto trans) with approx 172000 mi there's a nasty "booming/rumble" sound in the cabin above 42 mph. Not a shimmy or shake related to wheels/tires. I've tried coasting down a hill above 42 mph and slipping the trans into nuetral---and the "booming/rumble" continues....so it's not related to engine speed. I think it has to do with rear driveshaft speed. And I've heard that IF there's a u-joint issue, Subaru does not make u-joints available separately...they're happy to sell you an entire driveshaft assembly, however...

It is my opinion that FRONT axle shafts (still in good shape on this car) could not cause this because they're turning the same speed as the wheels---too slow to cause a booming vibration inside the car.

I guess what I'm really asking here is does anyone know if rear driveshaft or u-joint failure is a chronic problem with these cars as vehicle mileage gets way up there ??

[CNY_Dave]

The noise you describe is consistent with U-joint failures I've had on other cars.

 

It'll happen eventually to almost any car with a driveshaft.

 

If you can get under the car you can usually see the bad joint of you can grab the shaft to either side of the joint and turn one side one way, the other the other.

 

Also, if there is a lot of red rust around the joint, it's probably bad.

 

Dave

[Rooster2]

Same thought.........it is prolly a bad U-Joint on the drive shaft. Not a chronic problem on Subies. Just like any other U-joint on any car with a drive shaft, they eventually wear out.

 

Best to get it fixed soon. You don't want to have that U-joint shed its needle bearing to lock up, and physically break, causing the drive shaft to disconnect. That causes a highway break down requiring a tow truck to get you home.

[Fairtax4me]

Check the driveshaft and both rear wheel bearings for play. This could be either one.

[naru]

I`ve heard bad driveshaft steady bearing mounts make the exact same sound on other cars.

 

Grab the shaft near the bearing and see if it moves around.

[WoodsWagon]

Replacement joints are available from Rockford Driveline. They take a bit more work because the stock ones are staked in instead of held in by clips, so you have to grind a bit to clean things up, but the Rockford ones work well.

 

If you ignore it and the joint breaks, the flailing end of the driveshaft can cause a lot of damage. I had a friend get the whole shifter punched up through the center console when the front-most joint broke on his Forester.