06 OBXT Shudder

[keenan.corbett]

Hi guys,

Long time lurker, first time poster here. I am sorry if this has been covered many times, I have read and tried everything I could to solve my problem to no avail.

I have a 2006 OBXT and have been fighting with a vibration under throttle for about a year now. It only happens at and above 120km/hr, and ONLY on a right hand turn, be it very slight or sharp. Car drives very smooth and normal in all other cases, but when turning right, and applying any throttle (absolutely no issue when off the throttle) the whole front end starts shuddering violently, to the point where all I can do is let off the throttle completely, and it returns to normal.

I have replaced the following in the last year:

-Front wheel hub assemblies (wheel bearings)
-All tie rods
-Both front lower control arms
-Front Axles (Subaru) (2 times now because I was convinced they were the culprits, and the boots failed really quickly on the first set)
-Entire driveshaft assembly (Subaru)
-Tires & Alignment
-Front struts & Mounts
-Complete brake job including all rotors and pads
-Also had to replace the abs speed sensors since I broke them during the first axle change (Also now cruise control will run for about 1 minute, feels like its applying the throttle and backing off really fast, then shuts down and flashes, but this is a less important issue)

At this point I know I should have taken it in to the dealer and had them just fix it, but I am a huge DIY'er and have seen some really shoddy work performed at my local dealer, and I oroginally thought "It's a vibration. How hard/What could it possibly be..."

Sorry for the long post, but I am completely broken down by this car now. I have a road trip coming up this weekend, and absolutely cannot drive it in this condition. I am at a complete loss here, and don't know what else to do but hunt for insight. Any and all suggestions would be very very much appreciated.

Thank you,

Keenan

[Soledad]

You might check the motor mounts and possibly look into the front differential having issues. Maybe even try removing (or adding..can't remember) the fuse temporarily to make it FWD to see if the problem changes (if it's an automatic).

[catric69]

Have you inspected the following? ball-joints, bushings, steering rack...What condition are these items in?

[keenan.corbett]

Originally Posted by Soledad

You might check the motor mounts and possibly look into the front differential having issues. Maybe even try removing (or adding..can't remember) the fuse temporarily to make it FWD to see if the problem changes (if it's an automatic).

I'll check the motor mounts today, and at this point I'm really leaning towards a problem with the front diff. I will go try the awd disable right now.

[keenan.corbett]

Originally Posted by catric69

Have you inspected the following? ball-joints, bushing, steering rack...What condition are these items in?

I had all these items inspected after I replaced the tie rods and had the alignment done, and the reason I replaced the LCA's was because the large rubber bushings in each were cracked. Boots on the ball joints look fine, but I'm not sure how to check for excessive play.

[1 Lucky Texan]

wow, I'd guess you could inspect the magnets for the front and rear diffs for excess metal.

does your 06 have axle stubs? maybe one is not popped into place well.

try measuring the temps at the hubs with an infrared therm after a highway run. compare sides and if one side is 10-20 degs hotter, could be a bad bearing. (unlikely since off-throttle is OK)

[plain OM]

. . . the whole front end starts shuddering violently, to the point where all I can do is let off the throttle completely, and it returns to normal.

Do you have to let off the throttle completely, or just back it off a bit to slow the car to below 120 kph (75 mph)?

(Also now cruise control will run for about 1 minute, feels like its applying the throttle and backing off really fast, then shuts down and flashes, but this is a less important issue)

Not a rare problem after a wheel hub has been changed. There's a magnetic strip on the back of the hub that works with the ABS wheel sensor. There's been cases here where aftermarket hubs didn't seem to work well with these same Cruise Control symptoms. It's also possible that the strip was compromised by magnetic tools during installation.

I'm really leaning towards a problem with the front diff.

Hard to think of something in the differential that would impact only when the left axle is turning slightly faster than the right (as in a long slow right turn on a high speed highway) and not show up when doing the same (or a sharper turn) toward the left, or at speeds below 120 kph (75 mph).

I will go try the awd disable right now.

06 turbo has the 5-speed AT; the AWD disabling fuse might not work with this transmission. See if the "AWD" light comes on in the instrument panel.

Is the shuddering a violent shaking of the steering wheel, which would tend to localize the cause to the front, or is it felt in the car body itself?

[1 Lucky Texan]

Originally Posted by plain OM

Is the shuddering a violent shaking of the steering wheel, which would tend to localize the cause to the front, or is it felt in the car body itself?

great question

[keenan.corbett]

Originally Posted by 1 Lucky Texan

great question

The steering wheel vibrates pretty hard over 120, but the violent shudder is NOT felt through the wheel. It's felt through the floor.

[1 Lucky Texan]

have you tried moving the tires front to back?

after a warm-up run on the highway, would the car idle through some tight donuts on a flat dry, paved parking lot without jerking or requiring pressing the gas pedal?