Torque bind and slight steering wheel vibration just started after a 4 hour drive. 1999 manual Legacy

[kevinrse]

Hello all,

 

I have posted a lot here recently during two major jobs---replaced my clutch and did front end work, and later replaced timing belt. During these repairs, I also cleaned & re-packed my CV boots, changed transmission fluid (manual), and changed tie rod boots. I mention this since it might be relevant to my brand new problem, described below:

 

I got the thing running again after the timing belt job, and took a victory trip of about 4 hours highway driving today, at the start of a vacation. During the trip I noticed some very minor steering wheel shudder on the interstate. Once I got off the highway and pulled into a gas station, I realized there was a significant vibration/shudder during tight right & left turns at low speeds. Feels like torque bind based on what I've read about it. But, I'm not experienced enough to be sure---perhaps it could be something else.

 

I did some reading and noticed that (if it's torque bind) it could be my center differential viscous coupling. (I sure hope it isn't!) Relevant to this, I should point out that my transmission fluid was changed recently---but this problem didn't occur until AFTER this long trip. (I've heard/read that in old or poorly maintained cars, changing transmission fluid can cause problems).

 

I did check my tire pressure to make sure this isn't being caused by low tire pressure. I've got 35 psi on the left, and 30 and 32 on the right side. I imagine this isn't enough to cause torque bind. Could I be wrong?

 

I know I should have gotten an alignment done after the front end work, but I forgot to get it scheduled before this vacation. I figured it would probably be OK, since I counted threads when I was removing my tie rods and the vehicle isn't "pulling" to one side. I don't know if a slight misalignment could contribute to this.

 

Also, after my clutch job, I experienced some bearing noise after a few minutes of driving. Eventually I discovered that this can occur if axle nuts are over tightened (this prevents bearings from being able to expand when they heat up). I loosened the nuts a bit and the problem went away. Now I am wondering if today's problem could be the result of the bearings being *much* hotter than they are in driving around town (i.e., 4 hours of driving 75mph). Could it be worth loosening the axle nuts?

 

Finally, could the steering wheel shudder be related to the torque binding? Or are they probably unrelated problems?

 

As always, thanks to all the brilliant Subaru experts who have helped me out on this forum. Much obliged :-)

[rdweninger]

I have never heard of loosen axle nuts to 'fix' a problem.    You best torque them back to the 145-150 lbs as required by Subaru law.

That's where your wheel shudder is coming from... and a whole bunch of other problems if you don't get them torqued up soon !

make sure all tires are the same size and have approximately the same tread depth to prevent what you call torque binding.

[1 Lucky Texan]

typically, torque bind would be least noticeable in traveling straight, most noticeable in tight maneuvering.

 

get on level dry pavement (not gravel or dirt), crank the wheel hard left or right, do some slow circles. maybe try some slow figure 8s too. Jerkiness, maybe eventually needing to give more gas to move the car, point to torque bind.

 

Is this an auto or 5spd? remind us what car you have.

[Fairtax4me]

99 manual trans

 

Changing trans fluid doesn't hurt a manual. It can cause problems in poorly maintained automatics.

 

The shudder could be many things. I would have to suspect it to be bearing related. These need to be torqued to 140 ft lbs. Loosening them is very bad and will cause damage to the bearing.

[1 Lucky Texan]

manual trans seem to exhibit TB worse after being heated during a long run so, I'd say that's likely what the problem was.

[kevinrse]

Hi 1 Lucky Texan. I kept an eye on things after this post and the problem didn't re-emerge again.... until a few days ago. Same thing---long drive on the highway, TB happened at end of trip when I got off the highway.

 

Per others' comments in this thread regarding bearings/axle nuts: A former mechanic friend whose opinion I trust immensely said that yes, "loosening" axle nuts is often necessary to prevent bearings from binding up when they expand. This was consistent with my experience a long time ago---immediately after I repacked my CV joints during clutch replacement, car would shudder after several minutes highway speed. By "loosening" I am talking about torquing to spec (140-150 ft-lbs) and then backing off axle nut by 1/4 turn. This was echoed by my friend, an experienced Advance Auto Parts clerk, and one person elsewhere on this forum. It solved the problem then, and I have not had issues since---so this is a non-issue here. (Furthermore, TB only manifests when making tight turns. If it were bearings it would happen all the time).

 

So, my only question for 1 Lucky Texan is: Is this TB a symptom of some other problem? Or is it simply something that happens when a manual heats up over the course of a long highway drive? Should I be worried? Can I do anything to prevent it?

[1 Lucky Texan]

I have read of people experiencing jerky/TB-like symptoms from bad u-joints and maybe bad carrier bearings. But not from wheel bearings. I suppose it's possible. Even a stuck  and dragging brake caliper might behave oddly.

 

If, when the symptom does show-up, turning tight circles on flat dry pavement was quite a bit worse than driving straight - I'd say that would point to the center diff fairly conclusively. Also, I'd expect a wheel bearing that was binding due to heat might be a measurably warmer than it's mate (same with a dragging brake)  so, when the problem next arises, perhaps compare temps side-to-side with an infrared thermometer. They are cheap. Take some measurements when the problem is NOT present as well as when it is - sorta log normal vs failure conditions.

 

Have the driveline checked out.

 

maybe someone else will have some ideas.

Edited July 24, 2014 by 1 Lucky Texan

[idosubaru]

to the TB:

 

1.  are the tires all the same exact size?

2.  are any of the tires significantly different tread depth (new verses bald)?
3.  different gear ratio front and rear differentials will cause binding while driving straight - and would indeed get really bad making up all that difference during highspeed driving.

that would be caused by a transmission or rear differential being swapped from another vehicle (Impreza) with a different gear ratio.  3.9 and 4.11 are the two Subaru gear ratios of manuals.

4.  the center VLSD could be on it's way out - are you experiencing any binding at all around town on tight turns?  or it's ***only*** after highway driving?

 

 

That 1/4 turn wheel bearing notion is doubtful to be an issue in your case so not a big deal to move on- it's torqued three digits and staked, probably not going anywhere or causing issue. But that doesn't mean it's a good idea, one-size-fits-all suggestions are usually weak and show lack of experience. It may help in some cases, but will hurt in others. It would not be recommendable on Subarus. Wheel bearings differ - applying a one-size-fits-all approach across multiple decades of bearing changes, generations, manufacturers, and styles of wheel bearings, axles, and axle nuts with varying failure modes shows a short a limited view and experience.

 

There are vehicles with sensitive wheel bearings that would fail if you applied this approach. 

 

A more accurate saying might be, "loosening 1/4 turn on XYZ years of ABC model vehicles" is helpful.  But if someone can't explain what vehicles a technique is good for and which vehicles to not use it on - they aren't very well versed in what they're talking about and you should ask someone more familiar with the exact platform you're servicing.

[idosubaru]

If yo'ure still unsure of the diagnoses - I'd almost start over and give us a very clear description:
 

WHAT is it doing

WHEN is it doing it exactly

 

Be specific and technical, not tell stories or have extraneous details.  ALl we have is words so the better chosen they are the more we can help!

[kevinrse]

Great, thank you for the advice. Sounds like almost certainly center diff.

 

Is the center diff actively harming my drive train even when i am driving straight? hope i have not risked further damage. There have only been two times that TB has occurred, both after long highway drive, and only on tight turns on flat dry pavement as you said.

 

I'll see if it happens around town here the next couple of days and check with a thermometer.

 

I have been cautious to always use same tires on this vehicle, but it's at 230k and i've only owned it for 30k. I guess it was bound to happen someday. *sigh*...

 

Thanks again Texan. I will report back with progress. Anyone else with ideas much appreciated!!

[1 Lucky Texan]

I think that torque procedure you mentioned is for spindles with cone bearings ???? I recall something similar when I replaced a bearing on the rear of a FWD Honda Civic MANY years ago.

 

torque to X, back off, finger tight, cotter pin. - well, something like that lol!

[idosubaru]

Ah okay - it's not happening "during" long highway trips - but "after"?

 

In that case, it's likely the front VLSD.   You need a new VLSD installed.

very roughly $500 parts, $400 - $800 labor.

 

The binding itself does damage the drivetrain - it's putting stresses on the ujoints, rear diff, axles, and tires. That braking feeling you get around turns is all of those components binding up.  They're resilient and it would take some time for something to break, but I don't recommend ignoring it for long periods of time.

[kevinrse]

The above reply was for Texan. Thanks Grossgary, here are responses to your questions:

 

1.  are the tires all the same exact size?

All tires were installed brand new same time and are same type.

 

2.  are any of the tires significantly different tread depth (new verses bald)?

Left front - 0.192"

Right front - 0.157"

Left rear - 0.262"

Right rear - 0.255"

Could this be enough to have worn out my diff?

 

3.  different gear ratio front and rear differentials will cause binding...

I have no way of knowing this for sure, but I have owned the vehicle from 198k to 230k miles. I haven't done that. This problem only appeared in the last 1k or 2k miles. I have taken it on very long trips before without the TB occurring.

 

4.  the center VLSD could be on it's way out - are you experiencing any binding at all around town on tight turns?  or it's ***only*** after highway driving?

Nope, it is ONLY after highway driving. It is quite noticeable when it happens, very jerky. Doesn't happen at all driving around town.

 

Loosening 1/4 turn was done only after the bearings were binding---i.e. in response to that issue. Again, it's definitely a separate issue, but I do appreciate the thoughts on that. Trust me, I was fully cognizant that I did not want to undertighten those nuts. ;-) I drove around town for miles, loosening by tiny fractions of a turn, until the issue went away. Anyways, thanks again for this cautionary advice.

 

If details I provided were extraneous, it was only because I thought they might hold some relevance. Sorry for my noob questions. I really appreciate the help you have offered me here and in other threads!

[kevinrse]

Oops, keep falling behind on replies.

 

Texan - Not sure if my Subie is spindles w/ cone bearings... sorry, I'm bad on all this terminology. Trying to figure out via Google but can't make heads or tails of search results.

 

Grossgary - well, "during" and "after" could mean a couple of different things. It definitely cannot happen "during" a highway trip because it's only during tight, low-speed turns as I said. No shudder whatsoever on straight turns or curves on roads. If I pull off the highway after a couple of hours continuous driving, and I make a very tight turn e.g. in a gas station parking lot while the car is still hot, that's when it happens.

[kevinrse]

Grossgary thinks it's most likely VLSD---Texan thinks it is probably center diff.... how would I go about testing to determine which one is to blame?

 

Thanks again!

[1 Lucky Texan]

sorry, those terms mean the same thing for this discussion.

 

GG has a experience with this stuff so, he can probably advise you better how to proceed. I just read about stuff.

[kevinrse]

Gotcha. I got confused by the words "center" and "front" assuming they referred to two different components. Makes more sense now.

 

Since I have done my clutch already, I feel moderately comfortable trying to replace the differential on my own. I'll commence Youtube and Haynes manual research on this matter. Any advice on good source for the replacement part? Ebay? Subaru dealer? Other?

[idosubaru]

If you've driven it tens of thousands of miles then the final drive ratios have to match and that shouldn't be the cause.  Which points to the VLSD (Center differential).

 

Pretty sure it's a Subaru only part so if you get it from Ebay it'll simply be an online Subaru OEM parts dealer.  Options are used or new Subaru unit.

[1 Lucky Texan]

If i recall, your car has a lot of miles on it right?

 

you might consider an entire transmission from a wreck - might only have 1/4 the miles your present trans has on it.

[johnceggleston]

the tire size difference is not huge,

but it could be right at .26" if you are running stock tires and they are new.

and as the tire wears down, like now, the tread difference becomes a larger percentage.

this puts it is on the outer edge of what is acceptable,

all tires within 1/4 inch of circumference.

 

swap the front and rear tires on one side of the car.

this puts one big one and one small one on the front,

and one of each on the rear.

this should help even out the tire size difference.

 

if tire size is playing a part,

it could be that binding does not start until the fluid heats up on the hiway run.

and since the tire size difference is minor, the binding is minor?

and only shows up after a drive.

driving around town may not heat it up enough to cause noticeable binding.

 

if the front and rear diff ratios were different, the car would bind up so bad it would not move,

and it would do it fairly quickly, as soon as the viscous fluid heated up.

 

swap front to rear on one side of the car and see if it improves.

are all 4 tires inflated the same?

 

i do not know a whole lot about the manual trans,

but it was my understanding that when they went bad and started binding they did it all the time.

this leads me to believe that the tires size is playing a part.

and that the longer you drive it the hotter the fluid gets,

and the more binding you have.

 

of course the center diff could be going out as well.

 

good luck.

Edited July 24, 2014 by johnceggleston

[1 Lucky Texan]

I think people DO get binding all the time eventually. But I have read more than once of them binding, or binding worse, after heating-up. Some speculation is, the seals fail and GL-5 begins infiltrating the silicone/w'ever fluid in the viscous unit. If it really is a gradual process, it make sense it may be worse at some temperature extreme I guess.

 

hmmm, wonder if an oil analysis would find silicone in the GL-5 ?

[MilesFox]

typically, torque bind would be least noticeable in traveling straight, most noticeable in tight maneuvering.

 

get on level dry pavement (not gravel or dirt), crank the wheel hard left or right, do some slow circles. maybe try some slow figure 8s too. Jerkiness, maybe eventually needing to give more gas to move the car, point to torque bind.

 

Is this an auto or 5spd? remind us what car you have.

 

What kind of fluid was used? Subaru requires 'extra s' fluid in 80w90 or 75w140 (LSD) for the synchros to work properly. The center diff is viscous, and perhaps it's sticking. I suggest changing with subaru branded oil or equivalent and then go drive in tight circles.

[1 Lucky Texan]

that center Viscous Locking Limited Slip Differential's viscous unit in the 5spd is sealed and normally would be unaffected by the GL-5 in the rest of the trans/front diff part of the case. There may be more than one way it can fail, but from what I've read, the seal usually leaks and the special fluid inside starts mixing with the trans fluid.

 

 

on the right (with all the plates inside);

 

 

 

 

 

number 11 in this trans diagram;

 

Edited July 25, 2014 by 1 Lucky Texan

[Fairtax4me]

that center Viscous Locking Limited Slip Differential's viscous unit in the 5spd is sealed and normally would be unaffected by the GL-5 in the rest of the trans/front diff part of the case. There may be more than one way it can fail, but from what I've read, the seal usually leaks and the special fluid inside starts mixing with the trans fluid.

 

I would think gear oil is much lighter than the silicone fluid in the center diff, and would not have the same shear resistance properties, especially when warm.

Heating of the silicone fluid in the diff causes it to resist movement. As the plates in the diff spin past each other it creates a shearing effect of the fluid, and the fluid essentially thickens in order to prevent that.

Long term affects of the constant movement of the plates in the diff cause the fluid to break down and thicken, which will cause it to essentially lock the center diff even when it's cold.

 

Since the unit is sealed, the gear oil in the trans has no effect on it.