Shudder on low speed turns

[Gardener]

Hello, my ‘05 Impreza Sport Wagon with auto transmission makes a kind of shudder on tight turns at low speeds. It’s more of a vibration than a noise and seems to come from the rear wheels. I’ve had the car for 3 years and it’s always done it when parking but it seems to be getting worse. It reminds me of a much worse problem on a different Subaru when I installed mismatched tires but this car has the right sized tires properly inflated. The local repair shop says it’s “normal”!

 Thanks 

[1 Lucky Texan]

size is good but really, tires should be 'identical' - same brand, model, AND size of course, and near each other in wear level. Same size but different model is no good - identical.

 

that said, some folks have done 3 trans fluid drain/fill/drive a few days - type cycles and had luck freeing-up gummy deposits that may interfere with solenoid/valve operation.

the clutch pack in the tail section of the transmission may be bad.

under the hood in the fuse box there should be a spot for a spare fuse - any size fuse - that puts the car in FWD mode, you could try that as a diagnostic and temporary fix.

 

you are experiencing 'torque bind' , but it isn't clear yet why.

 

Edited July 6, 2018 by 1 Lucky Texan

[montana tom]

Its hard to say at this point , but your having early symptoms of torque bind.     

Install the fwd fuse and try. 

EDIT)   Great minds think alike Tex

Edited July 6, 2018 by montana tom

[Gardener]

Thanks so much Tex and Montana! I’m sorry to be slow replying, I thought I’d get an email when someone answered. Maybe my settings are wrong. Anyway, the tires are identical, purchased and installed at the same time. I had no idea about the FWD fuse! I will try that. And to be sure I understand, it’s the automatic transmission fluid you’re referring to, right? Not the gear oil in the differentials. 

Thanks again!

[montana tom]

Yup ,he's talking transmission oil.  Diff. oil wouldn't do this.

If your considering a trans fluid flush, here is an easy way.

Buy 3 gal atf..  Disconnect a cooler line at radiator. Place  line in empty gal jug . Start motor , idle as gal jug fills. Stop. empty used jug. replace under hose , pour one gal of new atf in at top. Repeat . By the 3rd gal you should be getting clean oil . 

[Gardener]

Thanks, I'll try it!

[Gardener]

So, putting a fuse in the FWD slot caused an amber AWD light to appear on the dash and the torque bind went away! This weekend I'll do the ATF changes and see what happens.

Thanks!

[montana tom]

good luck, hope it helps!

[1 Lucky Texan]

just FYI, it's OK to drive with the FWD fuse in as long as you need, just remember that on actual slippery/poor surfaces, you have no AWD ability.

this car never had a replacement rear diff or transmission did it? Mismatched final drive ratios will cause torque bind. You said it has done this your entire ownership? Wonder if the previous owner swapped a mismatched unit into the drivetrain.

 

[Gardener]

Thanks, I was wondering if it was ok to leave it in FWD. interesting thought about the previous owner! I don’t think I can contact him, any way to tell from the outside? The car only has 129000 miles and the symptoms have very gradually worsened. 

[Mike104]

I believe the Duty C solenoid is not rated for continuous use so it may be possible that at some point with the FWD fuse in the solenoid may burn out and the torque bind may return, but that's just an uneducated supposition.

[idosubaru]

Change the fluid.  If you're doing a drain and refill - usually it takes like 3 of them.  It's very common for this to alleviate initial signs of torque bind.  If it's just recently gotten worse I think you have a good chance of getting out of this with a few drain/refills. 

Mismatched diff ratio might be worth checking but usually cause very notable issues and are just consistently bad until the issue is alleviate - i wouldn't expect it to be drivable for 3 years and only now getting worse. 

I would run FWD indefinitely without concern.  I've done it and it's been done plenty of times and there's almost no real world feedback it causes issues - i've never seen or heard of it. 

What there are issues from is driving with torque bind - that definitely causes failure modes including sheared off drums inside the rear extension housing.  

[1 Lucky Texan]

probably have to confirm some numbers off the trans and rear diff

 

or, confirm proper tire pressure, go to some big parking lot/abandoned road, mark the tires with chalk at the bottom, drive straight for - 10 (?) or so revolutions of a tire, then compare front and rear tire chalk marks.

 

if rears are 'significantly' off from the fronts (over 2 inches or so ???) further investigation may be needed.

 

but if it wasn't severe and has been deteriorating, it may just be some buildup of deposits or odd failure of the duty c vlave or the wet clutch pack? The 'basket' in the clutchpack can have roughness/grooves worn into it and may not release the clutches well. maybe a previous owner negectfully drove with mismatched tires and damaged the clutch pack unit....?

Edited July 12, 2018 by 1 Lucky Texan