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Transmission questions


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17 replies to this topic

#1 mdjdc

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Posted 10 June 2008 - 08:32 AM

I have a 96 outback with the 2.5 dohc and auto transmission. When I first got the car it had 250k on the drivetrain and the engine had a slight bearing noise. The engine has been replaced with one with only 120k on it and that one is quiet as a church mouse. When I am driving at times the transmission will stutter between 2nd and 3rd gears. It is not a consistent stutter, but if I put the A/C on it gets worse. My mechanic says that is a sign of some type of engine involvement, possibly wires or coilpack. Does anyone have any other ideas? I'm going on vacation soon and I want to be secure in this car. I have another trans with 120k on it that I could swap into the car if needed. I just want to chase down all of the possible causes first.

Thanks in advance

Mike

#2 grossgary

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Posted 10 June 2008 - 08:47 AM

first questions are about tune up items:

plugs and wires
air filter, fuel filter, PCV valve
ATF change
O2 sensors are how old?
has the MAF sensor ever been cleaned or have you ever used a oil style filter?
timing belt is probably new since the engine went in?
what engine went in - solid lifters or HLA's? if solid - were they adjusted before the install?

coil pack could be suspect. if it does it all the time or consistently, i imagine you have others lying around to swap in place?

#3 mdjdc

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Posted 10 June 2008 - 09:02 AM

I'm going to replace the wires and swap out the coil pack today. I hadn't thought about the MAF, but I will clean that too. I guess I should just do a general tune up now.

The plugs are new and the engine is one with solid lifters. They weren't adjusted, but everything looked clean and free when I had it apart for new HG's before I put it in.

Thanks for the info.

Would you recommend against the K&N type filter? That is what is in it, but I can swap it out for a paper style filter.

#4 OB99W

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Posted 10 June 2008 - 09:10 AM

[...]When I am driving at times the transmission will stutter between 2nd and 3rd gears. It is not a consistent stutter, but if I put the A/C on it gets worse. My mechanic says that is a sign of some type of engine involvement, possibly wires or coilpack. Does anyone have any other ideas?[...]

If you haven't already done so, the first thing to do is verify that the trans fluid level is correct; it's not likely to cause what I think you're describing, but it's easy enough to check. (By the way, are you saying the 2-3 shift is rough, or that the trans "hunts" and can't seem to decide between 2nd and 3rd at times?)

A/C is an additional engine load that will change operating conditions seen by the ECU. The ECU and TCU communicate with each other, sharing sensor data, and it's certainly possible that engine-related issues can affect trans operation. Sufficiently severe problems will cause trouble codes to be generated, but subtler ones (that may still cause noticable drivability issues) often won't. Before assuming the trans is at fault, even if the CEL isn't lit, it may be worthwhile to scan for any pending codes.

Under rare conditions, electrical problems can cause the symptoms you've described. Look for any loose/corroded connections, especially grounds. Also, a quick check of the charging system might reveal something.

#5 grossgary

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Posted 10 June 2008 - 09:10 AM

if the wires are of unknown age then i'd be close to betting money it's the wires. i mean there are a lot of possibilities but EJ engines are very sensitive to plugs and wires.

Would you recommend against the K&N type filter? That is what is in it, but I can swap it out for a paper style filter.

i don't know. i've had good experience with them in the past. but it is said the oil carries to the MAF and can make it sticky, dirty, and attract dirt and cause problems. a friend of mine just had his replaced on his newer truck for a couple hundred dollars and he has a K&N on his. coincidence?? so i've avoided them for a few years.

they make MAF specific cleaner and any auto parts store should carry it, might want to make that part of your tune up.

#6 mdjdc

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Posted 10 June 2008 - 09:33 AM

The trans fluid level is right. I even had it flushed after the engine swap. The tranny doen't necessarily hunt for the next gear, stutters between shifts. Like it is bouncing back and forth for a second. It doesn't last long, but I want to be sure the tranny is working properly. I guess you might call the stutter a hunt. It doesn't have a hard or rough shift though. Once in gear the tranny works fine.

I'm going to go over the engine electrical and see if that fixes the problem. I guess I could swap out the TCU if necessary as I have one of those lying around too.

A friend of mine is a subie master mechanic and his son has a forester with the same tranny and 400k original on it and he says not to worry about it. Then again he isn't married to my wife and this is her car.

#7 johnceggleston

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Posted 10 June 2008 - 10:39 AM

have you tried shifting manually to see if it does it then?

or drive more aggressively in 2nd, and back off on the gas when it goes to 3rd. this may cause it to skip 3rd altogether, but who knows?

#8 mdjdc

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Posted 10 June 2008 - 11:17 AM

This is my wife's car and I only noticed the problem over the weekend when I had to use the A/C. She is kind of oblivious to car stuff and usually lets me know when something is broken.

#9 Gloyale

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Posted 10 June 2008 - 12:05 PM

Sounds pretty minor. I wouldn't worry much about it. Certainly doesn't seem like something that would lead to leaving you stranded.

#10 grossgary

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Posted 10 June 2008 - 01:47 PM

My XT6 4EAT had a stutter for a year or so since I got it, but drove and shifted fine, and now needs replacing. Mine seemed to sort of "stay" in between gears for a few seconds longer than what it needed to. Like it was in la-la land for second. But there dozens of reasons why a trans might do this.

If it is a problem, it's going to gradually become more apparent, not just randomly break down. Just make a mental note of it now and see what it's like down the road...unless it's getting more noticeable i wouldn't worry about it.

#11 johnceggleston

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Posted 11 June 2008 - 06:32 AM

somewhere i read an article about a hesitation shift, 2-3 maybe, and the cause being an engine sensor, i think, TPS maybe. the idea was the trans wasn't sure where the throtle was, once the sensor was replaced, all was fine. i guess you could try cleaning first. i wish i could remember.

#12 OB99W

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Posted 11 June 2008 - 07:31 AM

somewhere i read an article about a hesitation shift, 2-3 maybe, and the cause being an engine sensor, i think, TPS maybe. the idea was the trans wasn't sure where the throtle was[...]

Yes, as I mentioned previously, the ECU and TCU share sensor data. There's no question that the TPS data is used in determining shift characteristics, and bad data can cause problems. Sometimes when it's only off a small amount, or is intermittent, a trouble code won't be generated by the ECU or TCU even if the shift is affected.

#13 OB99W

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Posted 11 June 2008 - 07:42 AM

By the way, sometimes even dragging brakes can cause shift problems. For a situation causing 3-4 shift problems, read through this thread: http://www.ultimates...ead.php?t=85717

#14 mdjdc

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Posted 11 June 2008 - 07:46 AM

Thankfully the brakes have just been reworked and are in great shape. No dragging, so I will look at the other areas. The electronic issues may be why the mileage is lower than expected too.

#15 OB99W

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Posted 11 June 2008 - 08:03 AM

Thankfully the brakes have just been reworked and are in great shape. No dragging, so I will look at the other areas. The electronic issues may be why the mileage is lower than expected too.

You hadn't previously mentioned gas mileage issues in this thread. That's a good reason to verify the state of tune as others have suggested, but are you sure that the brake work was top quality? Even slight drag can sometimes cause shift problems. If you haven't done so, you might want to read the thread I linked to above.

#16 mdjdc

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Posted 11 June 2008 - 09:03 AM

Remember, this is my wife's car and she is a little heavy footed. I get better mileage in my 99 ob wagon 5spd, but I am not on it like she is. She jokes that if you want a tranny tested, just let her drive it for a week. Her first car was a honda four banger and she learned to romp it just to get out into traffic and the habit is now ingrained.

I did the brake work myself and the calipers are free and the ebrake properly adjusted. I really need to replace the leading O2 sensor and possibly swap out the TPS with another I have. Do I need to swap the whole throttle body, or can I just swap the sensor. If is easier to do the whole throttle body due to adjustments in the TPS, then that is what I will do tomorrow.

By the way, I really appreciate all of the great tips you guys are giving me.

Thanks

Mike

#17 grossgary

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Posted 11 June 2008 - 01:20 PM

mike - swapping the TPS isn't that hard at all and is easier except for the adjustment of course.

swapping throttle bodies can be annoying...forget how the EJ is set up but you have coolant lines, throttle cables, TPS, and a gasket to remove and replace to swap TB's. like you said, there's no adjusting then just bolt and go.

not that hard, so maybe it's worth it to avoid adjusting the TPS. i'd skim the FSM and make your decision based on how simple it looks there.

typically TPS adjustment is by voltmeter measuring of the TPS outputs or just do it visually. the TPS should just start to engage as the butterly plate opens.

don't know if you can do it on EJ's (haven't had to yet) but on older subaru's you can do it by ear with the engine running.

#18 mdjdc

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Posted 13 June 2008 - 08:49 AM

Hey Guys:

Thanks for all of the suggestions. Yesterday I replaced the plug wires (plugs were new), the O2 sensor with new ones. I swapped out the coil pack and TPS with younger ones and the car shifts like a dream now. While I was there I also replaced the differential fluids. Evidently the previous owner didn't believe in routine maintanence. Slowly but surely I'm replacing worn elements of this car. It's a nice car and my wife really likes driving it.

Once again, Thanks for the help.




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