[FOX-]

Lately I've been feeling a shudder at freeway speeds. It happens mostly between 60-75 mph. Once I get above 80 mph it seems to slow down or stop. It feels almost like a shift but my RPMs stay the same. It varies in harshness and frequency. Sometime it will happen once in a couple of miles, other times it will happen 5 or more times in a row. So far the MIL light has not come on.

A short history of the week leading up to it: I got a flat tire and drove home less than 10 miles on the spare in city traffic not going much faster than 35-40mph. I drove on my studded winter tires for 4 days while I waited for a shaved down tire from TireRack. I didn't notice anything with my studded tires but the ride isn't as smooth as my summer tires. I also installed a Primitive rear differential protector using the stock mounting bolts. I have since taken the rear protector off and the problem continues.

The car is a 2002 Outback Sedan with the H6 and VDC. Approximately 122k on the clock.

Thank you for any help.

-Tim

 

[FOX-]

After talking to my brother (A mechanic for a Subaru dealer on the East coast) he said my problem sounds like Torque Converter Shudder. He suggested I do a flush on the transmission. I had that done today, a drain and fill has been on my list of to do's anyway. I took the freeway home and it was still doing it but perhaps a bit less. I added a tube of friction modifier to the transmission and took another drive on the freeway and the problem persists. I'll drive it a couple more days and see if there is any change.

Any suggestions of what else it could be? Is there an external connector for the torque converter clutch solenoid? Disconnecting it should let me determine if it's actually the torque converter engaging or not.

Thank you,
-Tim

 

[cardoc]

I don't think its transmission or torque converter related. The torque converter will lock up and stay locked up. If there were any slippage, it wouldn't be at a specific speed range, it would be all the time.

The most common causes of highway vibration/shudder that occurs at speed are tire balance, alignment, uneven tire pressure and unequal tire wear between the four wheels.

Your sedan is AWD all the time, not like the other Gen 2 vehicles that are predominately FWD. Anything that may cause stress on the wheel assembly will cause the vibration and shudder. So, I would have the tires checked as well as the alignment. You would be surprised at what 3 psi difference will cause on these VDC's.

 

[FOX-]

I had that thought as well. I should feel a shudder once and it should be fine until I change speeds again. That's not the case, it will happen multiple times over a few minutes while cruising at approximately the same speed over relatively level ground. I also don't feel it at slower speeds.

Does anyone have a link to the conditions for the torque converter to lock? Is it only in 4th gear? Is there a speed range?

I'll make sure all the tires are at the right pressure tonight on my way to work. I think my replacement might be a couple of pounds off. I was going to do it this weekend when I removed the rear differential protector but I only want to change one thing at a time so I know what the problem was.

I need to replace the boots on my steering rack so I'll get an alignment done after that. Hopefully I can get that done this weekend.

I was also thinking about the possibility of the propeller shaft u-joints failing. I looked for the rust I've heard described here before but when the rain stops for a bit I might crawl under there and really shake some stuff around. If it was the U-joints I should be feeling it at slows speeds too?

-Tim

 

[cardoc]

I haven't been able to find a graph for TCC lock. On the VDC, the ECM controls the TCC lockup at various speeds when in "D". The programming used the TCC lockup to assist in braking and will keep the TCC locked as much as possible to assist in fuel economy, even on uphill slopes. On mine, the TCC is locked full on after 40 mph unless the ECM decides to unlock it for more torque transfer depending on the load detected.

The attachments are transmission related issue symptoms and probable causes. Notice that some of these list engine controls as probable culprits.

I am still not real clear on what you are trying to say it does. I thought you said it will start between certain speeds, then go away after 80.

Start with what you got. Look at the simple and sometimes overlooked. When my tire pressures differ, I get a shudder when the tires are "fighting" each other. Once the pressure is equal, no more shudder.

 

[FOX-]

So far I've only noticed it at freeway speeds above 60 mph, but most of my driving is either freeway or city traffic, no moderate speed country roads.

On the freeway I will feel a "bump". It almost feels like the transmission is shifting but maybe a bit harder of a shock. Sometimes it will just be a single "bump" other times I will feel it several times in a row. It feels like it's coming from the rear of the car but it's hard to tell with this sort of thing. I feel it through the body of the car. My passenger can feel it too. It's not a constant vibration. It happens and then it's gone until I feel it again. It will happen several times per mile. I feel it a lot less if I reach higher speeds. After about 80 MPH I stop noticing it.

ETA: It doesn't make any noise, at least nothing that I can hear over road noise.

-Tim

 

[FOX-]

On my way to work I made sure all the tires were inflated properly. On the freeway I still felt the same shuddering. I held onto the shift lever while I was driving and didn't feel any shock though the shifter, at least no more than I feel through my seat and the floor. I would imagine if it was coming from the transmission I would feel it more though the shifter. On the way home it did seem to shudder less often and less severely. If it is the transmission the new fluid may be working it's way into everything.

Cardoc, can you monitor the torque converter with you laptop?

I need to get under there and really take a look at the drive shaft. That's my next best guess.

-Tim

 

[cardoc]

The software I use on my laptop is Rom Raider and does not give me transmission data. I have to do the math according to gear ratios compared to engine loads and speed. I have a scan tool at the shop that will show Trans data, but for the cost of that scanner, you can buy another car.

Did you change the filter? It's in the left front fender behind the fog light.

The clunk is interesting. Have you checked the transmission mount? If the ECM is changing torque ratio when this happens, it may be either a harsh engagement, or the transmission is actually moving. A transmission shop will have the equipment to check line pressures and narrow it down.

Earlier this year I had my transmission rebuilt because of a harsh engagement caused by 2 things: a leaking seal and broken bearing. But, mine did it when it was cold and starting from a stop. It would "slam" forward after the engine rpm increased.

 

[FOX-]

I took a look at the drive shaft as best I could without raising it up to spin it. Everything looks visually good. I shook things around pretty hard and there doesn't appear to be any slop in the joints. The center bushing looks good and has some play in it but I assume that's it's purpose. The cat is in the way of the front u-joint but it looks good from what I can see, no rust or anything. I did notice a 3/4" band or so around the drive shaft where it might have come in contact with the large cat heat shield, but it seems to have only removed the paint.

Is that the Select Monitor made by Hitachi?

What would I look for with a bad transmission mount?

I'm really trying to explore all the options here. Would it be possible that I'm feeling a misfire and just not getting a code?

in any event I only felt it a few times on the way home this morning. It could be because it's been colder and it's temp related, or perhaps the transmission is finally adapting to the new fluid.

I talked to my brother again this morning. He thinks I should take another look at the axle I replaced.

I hate and love my car, so much.
-Tim

 

[cardoc]

I have a Genesis Evo with up to date software.

In order to check the transmission mount, you would need it lifted so you can do one of two things: use a long prybar to physically try to move the transmission up or have someone in the car with the brakes applied and have them give it throttle in gear to see if the torque moves it any substantial amount. The mount can look like its intact and still not be able to hold under load.

Yes, if the CV Axle is defective, it could be hanging up occasionally. Also, was the axle nut torqued down correctly?

No MIL light still?

 

[subiesailor]

Tires - go get them balanced

 

[FOX-]

I torqued the axle nut to 150 ft/lbs and then added a little more on top of that with a 3' breaker bar. I'm going to try to do some figure 8s in the parking lot at work tonight to listen for any issues.

I'm going to take a look at changing the plugs this weekend. They've been sitting in my garage for over a year, I just keep putting it off.

I might have the tires balanced when I get the alignment done. I would just really like to keep my "throwing money at the thing" to minimum right now. I have my studded tires already mounted on wheels. If I'm bored this weekend I might swap them out and see if I still have any issues.


I really appreciate all the help guys. I really want my car back to "normal".
-Tim

 

[plain OM]

A couple of notes, for whatever they're worth . . .

RomRaider Logger has been used by some of us to monitor/examine available 4EAT transmission PIDs (data). This includes the duty-cycle signal % for the torque converter lock-up solenoid. It can also log the signals to the shift solenoids. The actual PIDs that are available depends on the transmission and the TCM. See http://www.subaruoutback.org/forums/65-parts-accessories-performance/39426-freessm-complete-access-your-ecm-tcu.html for more info and, later in the thread, see the graphs that were generated from the recorded data. It might be challenging to capture a very short-term symptom, but it might be worth a try. Romraider Logger can also record engine PIDs (although not at the same time as the tranny), so that might be tried if there nothing in the transmission information.

Most of the discussion here seems to address a "vibration" as might be experienced due to an unbalanced wheel or drive shaft. However, my reading of the problem is that it might be more of a non-continuous bump or hesitation that repeats one or two times (perhaps more) and then stops. That doesn't seem characteristic of something that's rotating rapidly with an imbalance.

I don't have an alternative answer, but was wondering if fuel delivery could be an issue, especially as the car is an H6 that might have the fuel pump with the o-ring and cap that seems to pop out.

It's been a good discussion so far, and a lot of effort on the part of everyone. Hopefully it will lead to a resolution, soon . . .

 

[FOX-]

I ordered an OBD2 cable for my Netbook, it should be here Monday.

Yes, my symptoms are like you describe plain OM. I really don't think it's a rhythmic thing since I don't notice any pattern.

Is the fuel pump something I can inspect without dropping the fuel tank?

I picked up a bottle of fuel injector cleaner. I'll dump that in next time I fill up.

-Tim

 

[cardoc]

There are two pumps. Both accessable from under the back seat. The driver side pump moves fuel to the passenger side. The pass side pump feeds the engine. The harness plug for both is on the driver side tucked under a bracket and wrapped with insulation.

It would be easier to check pressure and flow at the return line on the fuel rail than pull the pump assembly. And if its not fuel related and you change the pump, your out the cost of the pump.

Sea Foam is the best fuel treatment to put in the tank. A full bottle with a tank of gas.

 

[plain OM]

There are two pumps.

I believe there's only one electrical pump, on the right side. The "pump" to transfer fuel from the left side to the right is "passive".

Fuel is transferred from the left side to the right using a jet pump (venturi principle). Fuel returning to the tank from the fuel pressure regulator in the engine compartment passes through the venturi, causing a relative low pressure, and thereby drawing fuel from the left side of the tank through a hose connected between the venturi and left side fuel level sensor assembly.

 

[cardoc]

Yes. You would be surprised at how many times a tech pulls Up the back seat, sees a cover plate, and removes the wrong pump, wasting his time. If a everyday tech does it, any one would.

Still check pressure and flow first.

 

[FOX-]

I haven't gotten a chance to dig into the fuel pump yet, but I have been doing more research on my issue.

I'm thinking it might be the throttle position sensor. It seems to be a common issue on my engine and this thread seems to describe my issues exactly. I think it's worth throwing the $100 at the problem to see if it goes away, especially if the sensor is going to fail soon anyway.

-Tim

 

[FOX-]

I replaced the TPS today. Hurricane Sandy had the part stuck in NJ for an extra week. I made a illustrated guide while I was at it. She runs and drives fine right now, I haven't had a chance to get her up to speed on the freeway yet. We'll see.

-Tim

 

[FOX-]

I'm still feeling the same hesitation or whatever it is. I pulled the fuel pump today, the cap on the fuel pump looks fine so that's not the issue. I'll probably have the spark plugs changed and go from there. I feel like I'm chasing a ghost. No MIL, no anomalies with my monitored data, if it wasn't for my GF feeling it too I would think I was going crazy.

On the plus side I am getting to know my car better.

-Tim