40 replies to this topic

[grossgary]

vehicle, engine, mileage?

 

if it does it when loaded, then how about suspension - struts, end links, bushings?

 

rear diffs on Subaru's never fail, i wouldn't let them rebuild it.  change the gear oil in it and see if any chunks/metal come out.

[sario]

vehicle, engine, mileage?

 

if it does it when loaded, then how about suspension - struts, end links, bushings?

 

rear diffs on Subaru's never fail, i wouldn't let them rebuild it.  change the gear oil in it and see if any chunks/metal come out.

 

 

 

1997 Outback

Auto

270,700

 

 The struts have around 50k and the rest of suspension components appear fine to my armature eye.  The car is no where near bottomed out, i have king springs on which really help with that.

[Fairtax4me]

I do have king springs on the car, so it sits about an 1.5" taller than normal. That might have something to do with my problem. Also I'm pretty sure the first two drive lines failed because i had tires that were having tread separation issues at speed. Do you think there is something else i should be checking for?

Spring height does not affect the driveshaft. The biggest factor leading to failure is u-joint angle. Usually because the center joint is either too high or too low in comparison to the front and rear joints.
Does your car have any lift blocks or spacers on the sub-frames? If so you need a spacer of the same height on the center driveshaft support.

The driveshafts also differ slightly between models. A legacy Outback driveshaft center support is designed to sit about 3/4" lower than a driveshaft from an L or GT model.

[sario]

Spring height does not affect the driveshaft. The biggest factor leading to failure is u-joint angle. Usually because the center joint is either too high or too low in comparison to the front and rear joints.
Does your car have any lift blocks or spacers on the sub-frames? If so you need a spacer of the same height on the center driveshaft support.

The driveshafts also differ slightly between models. A legacy Outback driveshaft center support is designed to sit about 3/4" lower than a driveshaft from an L or GT model.

I wish it had lifting blocks.  But no it doesn't

[Fairtax4me]

When you get these replacement driveshafts are you getting them from Outback models?

[sario]

I'm told they are, but I didn't pull the drive shafts myself.

[Fairtax4me]

They could be giving you the wrong driveshafts. Lengthwise an Outback and a base or L model driveshaft are the same. Only the center mount is different and may not appear so unless careful attention is paid to the mount.

With the correct driveshaft the u-joint angles are near 0 degrees. If you look at the driveshaft from the side of the car, it will appear to be parallel with the floor pan the entire way from front to back.
An incorrect driveshaft, in your case, would appear raised in the center, because the center mount is designed to place the driveshaft about an inh higher in the tunnel. This causes the u-joint angles to be excessive and will cause vibration and, there-fore, wear in the u-joints, leading to early failure.

Check to see if the driveshaft that's in the car looks straight, or if it raises toward the floor pan in the center.

[sario]

They could be giving you the wrong driveshafts. Lengthwise an Outback and a base or L model driveshaft are the same. Only the center mount is different and may not appear so unless careful attention is paid to the mount.

With the correct driveshaft the u-joint angles are near 0 degrees. If you look at the driveshaft from the side of the car, it will appear to be parallel with the floor pan the entire way from front to back.
An incorrect driveshaft, in your case, would appear raised in the center, because the center mount is designed to place the driveshaft about an inh higher in the tunnel. This causes the u-joint angles to be excessive and will cause vibration and, there-fore, wear in the u-joints, leading to early failure.

Check to see if the driveshaft that's in the car looks straight, or if it raises toward the floor pan in the center.

The drive line does appear to be  flat.  But while i was down there i noticed a loose nut on the transmission mount.  I don't know if this could be causing the problem, or caused by it.  But when i try to tighten the nut the stud just spins.

[presslab]

The stud shouldn't spin, it's part of the trans mount.  Maybe it was broken when the new mount was installed.

 

The gap is normal.

 

You'll notice your mount does not have as many studs as the one pictured below.  The new ones are like yours.

 

[sario]

Bummer, I guess I still don't have a lead on the problem then.

[presslab]

Well you should probably figure out why the stud spins...

[Fairtax4me]

It looks like someone broke the mount stud and put a bolt through it. There shouldn't be a giant washer on there, and that second stud looks about 1/2" longer than it needs to be. Not a big deal, but you'll want to see if you can get a wrench on the head of the bolt so you can tighten it.
Is that the cause of the vibration problem? Probably not. However, you should check the bolts that hold the cross member to the frame. Good chance those could be loose as well considering whoever repaired that mount left that bolt loose.

As for the vibration issue, still sounds like a driveshaft issue, but I suppose it could be an axle problem as well. 270k is a lot of miles for a stock axle and if you're towing with the car they are getting more than normal wear.

What happens if you put the FWD fuse in? Does the vibration get worse or go away?

[sario]

The problem is still there with the FWD in.  I'll check over the rear axles a little more, they are orginal.

 

 

EDIT: I was wrong, it does still do it with the FWD fuse in.   I just didn't have enough of a load on the car when i tried.

Edited by sario, 26 June 2013 - 07:48 AM.

[Fairtax4me]

If its still there when in FWD its probably one of the front axles.
If either has even been replaced with an aftermarket axle, I would suspect that one first.
Subaru axles have green paint on the axle cups.

[sario]

I was wrong, it does still do it with the FWD fuse in.   I just didn't have enough of a load on the car when i tried.

[sario]

While investigating this problem i found had a rear sticking brake caliper.  I rebuilt the calipers and the problem seems to have gone away. 
Also replaced the diff fluid,  maybe that was the problem.  Either way i'm happy.  Thanks for everyones help, and I'll report back if the problem reappears.