Initial acceleration vibration.

[billisa]

When starting from a standing stop, I noticed a vibration/shuddering that disappears at 8-10mph. I had the rear wheel bearings done, because they were noisy. The car is quiet now, but I'm not sure the vibration is gone. I can't tell for sure because we just got a snow storm, so the roads are not good for testing.

My mechanic thinks, if new wheel bearings haven't solved the issue, then there may be something in the driveline. It's definitely not engine related in terms of misfiring.

Also, every so often, it sounds like metal is hitting metal. Even at 1mph, you'll hear a "ting", but it isn't happening all the time. Like something hitting the exhaust. The shields were all tightened.

The vibration from 0 to 8mph just started this morning.

Is this binding? Is there something in the AWD system? Solenoids? The driveline itself seems tight. Motor mounts? A loose flywheel? Obviously I'm guessing.

Any help would be graciously accepted.

Thanks!

[mbtoloczko]

I had a driveshaft that would vibrate badly when accelerating at less than 10 mph. I could feel it right in the location of the shifter. Maybe a little behind.

[Earthworm]

I highly doubt binding as that's usually only noticable around corners. Perhaps the u-joints in the driveshaft are worn out.

[billisa]

My mechanic thought it could be the driveshaft. So, does this mean replacing the whole driveshaft, or is there another, simpler way? Just the U-joints? Someone also suggested transmission/motor mounts.

If it's the driveshaft, is there a good place to get one. 1stSubaru parts can get me one, but it has to be shipped to them from NJ to Seattle, then from Seattle to me. Supposedly, Subaru doesn't drop-ship.

Thanks for your help!

[mbtoloczko]

Before you go an buy a new driveshaft, first take a look at the rear tranny mount as Harvey suggested in your other thread. The mount has a tendency to age, crack, and tear apart. If this tears apart, that could cause some vibration too. If the rear tranny mount is ok, then move onto the driveshaft.

Some places can rebuild the SVX driveshaft. Lots of places don't like to mess with it though because the u-joints are "staked-in", so they were never mean't to be replaced. Your driveshaft has has u-joints at both ends and a CV joint in the middle.

First thing to do would be to have the driveshaft inspected for obvious wear/failure. Just so you are aware, because the u-joints on Subaru driveshafts undergo very little change in operating angle, the u-joints quickly develop a "notched" feel. Many driveshaft shops will interpret this as a worn out u-joint. What's important to observe is how loose the u-joint feels at its normal operating angle.

A new driveshaft from 1stsubaruparts.com is around $375. If you can find a place that will do a total rebuild and balance for $300 or less, then it would be worth considering over a new driveshaft.

[billisa]

First thing to do would be to have the driveshaft inspected for obvious wear/failure. Just so you are aware, because the u-joints on Subaru driveshafts undergo very little change in operating angle, the u-joints quickly develop a "notched" feel. Many driveshaft shops will interpret this as a worn out u-joint. What's important to observe is how loose the u-joint feels at its normal operating angle.

OK, my mechanic says he notices about 1" or so of play in what he's calling the "center hanger bearing" on the driveshaft. This apparently can be replaced, and he suspects it. BUT he has never worked on an SVX and wants to know how much play is normal in this bearing. He also correctly picked up the "notched" feel, but (on his own) said that seemed normal.

Also, how much play should be in the rear rubber mounts on the rear diff. He says these look pretty tight, and that overall the U-Joints are fine.

[mbtoloczko]

The center bearing is supported by a flexibile rubber sheet, so about an inch of "resistive" play is normal. Now if the center section is just flopping around all over the place with no resistance, then its in bad shape.

The rear diff should feel tight, but there is actually a bunch of free play back there. Its normal.

Have the mechanic get a good look at the rear rubber tranny mount. If he can put a jack under the tranny to try to lift it up a bit, then he can more easily see if the rubber mount is damaged.

[billisa]

OK, well it turned out to be a front U-Joint, necessitating a replacement of the entire driveshaft. A local Subaru expert advised against a remanufactured driveshaft, saying they'd had bad experience. So for a total of $719.00 I have a new driveshaft. I also put in new rear wheel bearings that had become very noisy. Feels very solid, and sounds very quiet. I think the U-Joint may have been going for a while...

Anyway, thanks for all the quick advise and help. It enabled my guy to avoid detours and get to the problem.

Thanks again. You all are great.