My 2001 H6 auto Outback has developed a mild shaking/noise when taking off from a start. Once underway there is no issue. There is no apparent bearing whine. It seems to come from the propshaft or rear or the transmission. Does not happen with gentle acceleration.

 

I looked under the car and could see the rubber bushing for the center bearing seems quite soft and the shaft sits towards the bottom, not centralized. I was wondering if it's just a matter of replacing that rubber support? There appears to be fresh scraping on the shaft where it might be touching the heat shield on take off (could not see clearly as I didn't have it on jackstands, just crawled underneath). 

 

This model does not have a FWD fuse, so I can't test it with no rear power. Any ideas?

 

Rod

It sounds like you may need a new (used) driveshaft due to a bad universal joint. As it is not making a vibration at speed that slowly gets lower with time, inspect that driveshaft now.

 

I am going to assume that its not a tire issue only because this can be a saftey issue. How many miles are on it.

 

FWD fuse isnt going to help at all if it is the drive shaft. 

It could also be failed engine-mounts.

 

When you give the engine some gas, the engine/transmission can physically move around a bit.

This can be seen/heard when flooring the gas, either from a start or while on the move.

 

What happens with the car in Drive, and all brakes on, if you give it some gas? Does the engine physically move up? 

I'll do the test on the engine mounts shortly. I thought the FWD mode might affect if it is the center mount as the high starting torque on the shaft might cause it to flex sideways, whereas when just driven by the rear wheels turning, there would be no torque to speak of.

 

Car has done 180k miles. Wouldn't a bad U joint cause vibration and perhaps noise all the time? The shudder sounds like a rotating member lightly hitting something - and fresh wear points as noted. I'l post a photo later. Thought of mounting my GoPro underneath to see if it records anything.

also, check the rear bushing for the front lower control arm(s). It's rubber with fluid filling but, they lose the fluid and can then begin to degrade. Febest has decent, affordable replacement at Amazon - maybe other places too.

Could be the rubber mounts for the rear diff too, thay are visible if you look from the rear.

There should be a FWD fuse, but after 99 or 2000 they moved it into the main fuse panel under the hood. Check there.

 

The rubber center supports are very soft, even brand new ones tend to hang down a bit.

 

I would suspect a bad u-joint. One of them may have seized or the grease has dried and its binding when its put under load.